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Sample records for bulk glass forming

  1. Forming of bulk metallic glass microcomponents

    DEFF Research Database (Denmark)

    Wert, John A.; Thomsen, Christian; Jensen, Rune Debel

    2009-01-01

    The present article considers forward extrusion, closed-die forging and backward extrusion processes for fabrication of individual microcomponents from two bulk metallic glass (BMG) compositions: Mg60Cu30Y10 and Zr44Cu40Ag8Al8. Two types of tooling were used in the present work: relatively massive...

  2. Thermoplastic Micro-Forming of Bulk Metallic Glasses: A Review

    Science.gov (United States)

    Li, Ning; Chen, Wen; Liu, Lin

    2016-04-01

    Bulk metallic glasses are a fascinating class of metallic alloys with an isotropic amorphous structure that is rapidly quenched from liquid melts. The absence of a crystalline micro-structure endows them with a portfolio of properties such as high strength, high elasticity, and excellent corrosion resistance. Whereas the limited plasticity and hence poor workability at ambient temperature impede the structural application of bulk metallic glasses, the unique superplasticity within the supercooled liquid region opens an alternative window of so-called thermoplastic forming, which allows precise and versatile net-shaping of complex geometries on length scales ranging from nanometers to centimeters that were previously unachievable with conventional crystalline metal processing. Thermoplastic forming not only breaks through the bottleneck of the manufacture of bulk metallic glasses at ambient temperature but also offers an alluring prospect in micro-engineering applications. This paper comprehensively reviews some pivotal aspects of bulk metallic glasses during thermoplastic micro-forming, including an in-depth understanding of the crystallization kinetics of bulk metallic glasses and the thermoplastic processing time window, the thermoplastic forming map that clarifies the relationship between the flow characteristics and the formability, the interfacial friction in micro-forming and novel forming methods to improve the formability, and the potential applications of the hot-embossed micro-patterns/components.

  3. Computational studies of the glass-forming ability of model bulk metallic glasses.

    Science.gov (United States)

    Zhang, Kai; Wang, Minglei; Papanikolaou, Stefanos; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2013-09-28

    Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate R(c) below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing R(c), and thus good glass-formers possess small values of R(c). We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change R(c) significantly. These results are tempered by the fact that the slowest cooling rates achieved in our simulations correspond to ~10(11) K/s, which is several orders of magnitude higher than R(c) for typical BMGs. Despite this, our studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.

  4. Computational studies of the glass-forming ability of model bulk metallic glasses

    Science.gov (United States)

    Zhang, Kai; Wang, Minglei; Papanikolaou, Stefanos; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2013-09-01

    Bulk metallic glasses (BMGs) are produced by rapidly thermally quenching supercooled liquid metal alloys below the glass transition temperature at rates much faster than the critical cooling rate Rc below which crystallization occurs. The glass-forming ability of BMGs increases with decreasing Rc, and thus good glass-formers possess small values of Rc. We perform molecular dynamics simulations of binary Lennard-Jones (LJ) mixtures to quantify how key parameters, such as the stoichiometry, particle size difference, attraction strength, and heat of mixing, influence the glass-formability of model BMGs. For binary LJ mixtures, we find that the best glass-forming mixtures possess atomic size ratios (small to large) less than 0.92 and stoichiometries near 50:50 by number. In addition, weaker attractive interactions between the smaller atoms facilitate glass formation, whereas negative heats of mixing (in the experimentally relevant regime) do not change Rc significantly. These results are tempered by the fact that the slowest cooling rates achieved in our simulations correspond to ˜1011 K/s, which is several orders of magnitude higher than Rc for typical BMGs. Despite this, our studies represent a first step in the development of computational methods for quantitatively predicting glass-formability.

  5. Bulk forming of industrial micro components in conventional metals and bulk metallic glasses

    DEFF Research Database (Denmark)

    Arentoft, Mogens; Paldan, Nikolas Aulin; Eriksen, Rasmus Solmer;

    2007-01-01

    For production of micro components in large numbers, forging is an interesting and challenging process. The conventional metals like silver, steel and aluminum often require multi-step processes, but high productivity and increased strength justify the investment. As an alternative, bulk metallic...... glasses will at elevated temperatures behave like a highly viscous liquid, which can easily form even complicated geometries in 1 step. The strengths and limitations of forming the 2 materials are analyzed for a micro 3D component in a silver alloy and an Mg-Cu-Y BMG. ©2007 American Institute of Physics...

  6. Glass-forming ability analysis of selected Fe-based bulk amorphous alloys

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    R. Nowosielski

    2010-09-01

    Full Text Available Purpose: The paper mainly aims to present the structure and thermal stability of selected Fe-based bulk metallic glasses: Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4.Design/methodology/approach: The investigated samples were cast in form of the rods by the pressure die casting method. The structure analysis of the studied materials in as-cast state was carried out using XRD and TEM methods. The thermal stability associated with glass transition temperature (Tg, onset (Tx and peak (Tp crystallization temperature was examined by differential scanning calorimetry (DSC. Several parameters have been used to determine the glass-forming ability of studied alloys. The parameters of GFA included reduced glass transition temperature (Trg, supercooled liquid region (ΔTx, the stability (S and (Kgl parameter.Findings: The XRD and TEM investigations revealed that the studied as-cast metallic glasses were fully amorphous. Changes of the onset and peak crystallization temperature and the glass transition temperature as a function of glassy samples thickness were stated. The good glass-forming ability (GFA enabled casting of the Fe72B20Si4Nb4 and Fe43Co14Ni14B20Si5Nb4 glassy rods.Practical implications: The obtained examination results confirm the utility of applied investigation methods in the thermal stability analysis of examined bulk amorphous alloys. It is evident that parameters Trg, ΔTx, Kgl, S could be used to determine glass-forming ability of studied bulk metallic glasses.Originality/value: The success of fabrication of studied Fe-based bulk metallic glasses in form of rods with diameter up to 3 mm is important for the future progress in research of this group of materials.

  7. In-situ study of crystallization kinetics in ternary bulk metallic glass alloys with different glass forming abilities

    Science.gov (United States)

    Lan, Si; Wei, Xiaoya; Zhou, Jie; Lu, Zhaoping; Wu, Xuelian; Feygenson, Mikhail; Neuefeind, Jörg; Wang, Xun-Li

    2014-11-01

    In-situ transmission electron microcopy and time-resolved neutron diffraction were used to study crystallization kinetics of two ternary bulk metallic glasses during isothermal annealing in the supercooled liquid region. It is found that the crystallization of Zr56Cu36Al8, an average glass former, follows continuous nucleation and growth, while that of Zr46Cu46Al8, a better glass former, is characterized by site-saturated nucleation, followed by slow growth. Possible mechanisms for the observed differences and the relationship to the glass forming ability are discussed.

  8. In-situ study of crystallization kinetics in ternary bulk metallic glass alloys with different glass forming abilities

    Energy Technology Data Exchange (ETDEWEB)

    Lan, Si; Wei, Xiaoya; Wu, Xuelian; Wang, Xun-Li, E-mail: xlwang@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, 83 Tat Chee Ave., Kowloon (Hong Kong); Zhou, Jie; Lu, Zhaoping [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing (China); Feygenson, Mikhail; Neuefeind, Jörg [Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States)

    2014-11-17

    In-situ transmission electron microcopy and time-resolved neutron diffraction were used to study crystallization kinetics of two ternary bulk metallic glasses during isothermal annealing in the supercooled liquid region. It is found that the crystallization of Zr{sub 56}Cu{sub 36}Al{sub 8}, an average glass former, follows continuous nucleation and growth, while that of Zr{sub 46}Cu{sub 46}Al{sub 8}, a better glass former, is characterized by site-saturated nucleation, followed by slow growth. Possible mechanisms for the observed differences and the relationship to the glass forming ability are discussed.

  9. Linking structure to fragility in bulk metallic glass-forming liquids

    Energy Technology Data Exchange (ETDEWEB)

    Wei, Shuai, E-mail: shuai.wei@asu.edu, E-mail: m.stolpe@mx.uni-saarland.de [Department of Materials Science and Engineering, Saarland University, Campus C63, 66123 Saarbrücken (Germany); Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287 (United States); Stolpe, Moritz, E-mail: shuai.wei@asu.edu, E-mail: m.stolpe@mx.uni-saarland.de; Gross, Oliver; Gallino, Isabella; Hembree, William; Busch, Ralf [Department of Materials Science and Engineering, Saarland University, Campus C63, 66123 Saarbrücken (Germany); Evenson, Zach [Department of Materials Science and Engineering, Saarland University, Campus C63, 66123 Saarbrücken (Germany); Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln (Germany); Bednarcik, Jozef [Deutsches Elektronen-Synchrotron DESY, Notkestrasse 85, D-22603 Hamburg (Germany); Kruzic, Jamie J. [Material Science, School of Mechanical, Industrial, and Manufacturing Engineering, Oregon State University, Corvallis, Oregon 97331 (United States)

    2015-05-04

    Using in-situ synchrotron X-ray scattering, we show that the structural evolution of various bulk metallic glass-forming liquids can be quantitatively connected to their viscosity behavior in the supercooled liquid near T{sub g}. The structural signature of fragility is identified as the temperature dependence of local dilatation on distinct key atomic length scales. A more fragile behavior results from a more pronounced thermally induced dilatation of the structure on a length scale of about 3 to 4 atomic diameters, coupled with shallower temperature dependence of structural changes in the nearest neighbor environment. These findings shed light on the structural origin of viscous slowdown during undercooling of bulk metallic glass-forming liquids and demonstrate the promise of predicting the properties of bulk metallic glasses from the atomic scale structure.

  10. Crystallization behavior of Fe- and Co-based bulk metallic glasses and their glass-forming ability

    Energy Technology Data Exchange (ETDEWEB)

    Louzguine-Luzgin, D.V., E-mail: dml@wpi-aimr.tohoku.ac.jp [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Bazlov, A.I. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); National University of Science and Technology “MISiS”, Moscow 119049 (Russian Federation); Ketov, S.V. [WPI Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Inoue, A. [International Institute of Green Materials, Josai International University, Togane 283-8555 (Japan); School of Materials Science and Engineering, Tianjin University, 300072 (China); Department of Physics, King Abdulaziz University, Jeddah 22254 (Saudi Arabia)

    2015-07-15

    In the present work we study and compare the crystallization behavior of Fe- and Co-based good bulk glass formers with an exceptionally high glass-forming ability leading to the critical thickness of cast samples reaching 1 cm. For Fe-based alloys we also investigate the effect of opposite C/B content ratio on the glass-forming ability and the crystallization behavior. The structure and phase composition of the glassy samples were examined by conventional X-ray diffractometry and transmission electron microscopy while thermal stability and phase transformations were studied by differential scanning calorimetry. The reasons for high glass-forming ability are discussed. The glass-forming ability of the studied alloys depends on both factors: the type of crystallization reaction and characteristic temperatures. - Highlights: • Crystallization of Fe-based and Co-based bulk glass-forming alloys. • The reasons for enhanced glass-forming ability of these alloys are discussed. • Low growth rate of χ-Fe{sub 36}Cr{sub 12}Mo{sub 10} phase. • Reduced liquidus temperature of Fe{sub 48}Cr{sub 15}Mo{sub 14}C{sub 6}B{sub 15}RE{sub 2} alloys.

  11. Formation and mechanical properties of bulk Cu-Ti-Zr-Ni metallic glasses with high glass forming ability

    Institute of Scientific and Technical Information of China (English)

    YANG Ying-jun; KANG Fu-wei; XING Da-wei; SUN Jian-fei; SHEN Qing-ke; SHEN Jun

    2007-01-01

    Bulk amorphous Cu52.5Ti30Zr11.5Ni6 and Cu53.1Ti31.4Zr9.5Ni6 alloys with a high glass forming ability can be quenched into single amorphous rods with a diameter of 5 mm, and exhibit a high fracture strength of 2 212 MPa and 2 184 MPa under compressive condition, respectively. The stress-strain curves show nearly 2% elastic strain limit, yet display no appreciable macroscopic plastic deformation prior to the catastrophic fracture due to highly localized shear bands. The present work shows clearly evidence of molten droplets besides well-developed vein patterns typical of bulk metallic glasses on the fracture surface, suggesting that localized melting induced by adiabatic heating may occur during the final failure event.

  12. Effects of B addition on glass forming ability and thermal behavior of FePC-based bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    Sheng-feng Guo; Chen Su; Jia-xiang Cui; Jing Li; Guan-nan Li; Meng Zhang; Ning Li

    2017-01-01

    The FePC-based bulk metallic glasses (BMGs) have been demonstrated to possess high plasticity and good soft magnetic properties.However, the relatively poor glass forming ability (GFA) and thermal stabilities limited their application in industries.The effects of microalloying with B in FePC-based BMGs on the GFA and thermal behaviors were systematically investigated.It was found that a small amount of B addition can dramatically enhance the GFA of FePC-based BMGs, which in turn leads to the critical maximum diameter up to 2 mm for full glass formation even using low cost raw materi-als.The underlying mechanism of the enhancement of GFA from the competing crystalline phase with amorphous phase, the average thermal expansion coefficient and dynamic viscosity were dis-cussed in detail.

  13. Insight on the glass-forming ability of Al–Y–Ni–Ce bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shih-Fan, E-mail: sfchen@ntut.edu.tw [Institute of Materials Science and Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China); Chen, Chih-Yuan, E-mail: chen6563@gmail.com [Department of Energy Engineering, National United University, Miaoli 36003, Taiwan (China); Lin, Chia-Hung [Institute of Materials Science and Engineering, National Taipei University of Technology, Taipei 106, Taiwan (China)

    2015-07-15

    Highlights: • Adding 1 at.% cerium to Al{sub 87}Y{sub 8}Ni{sub 5} alloy causes glass transition. • A large ΔT{sub x} indicates that (Al{sub 87}Y{sub 8}Ni{sub 5}){sub 99}Ce{sub 1} is possibly a ductile amorphous alloy. • Ce is effective in improving the thermal stability of the Al–Y–Ni amorphous alloy. • The hardness of the crystallized cerium-bearing alloy was as high as 593 Hv. - Abstract: In the present study, the role of Ce in the thermal stability and glass forming ability (GFA) of (Al{sub 87}Y{sub 8}Ni{sub 5}){sub 99}Ce{sub 1} alloy ribbons produced by a single roller melt-spinning process has been investigated in an attempt to understand the influences of multiple RE elements in an Al–TM–RE (TM: transition metal, RE: rear earth metal) alloy system. Only the (Al{sub 87}Y{sub 8}Ni{sub 5}){sub 99}Ce{sub 1} alloy ribbon showed a glass transition temperature (T{sub g}) at 483.2 K, and its ΔT{sub x} value was 41.3 K. Crystallization occurred in the temperature range of 500–750 K in three exothermic reaction stages. The peak temperature for these reactions shifted toward higher temperatures at higher heating rates. XRD and SEM analysis of annealed samples revealed that nano-sized Al particles precipitated within the amorphous matrix during the first exothermic reaction. The maximum hardness was obtained for both non-cerium and cerium addition alloys after crystallization in the 550–660 K region due to numerous nano-sized precipitates randomly and homogeneously distributed in the amorphous matrix. Moreover, from observation of the fracture surface, it is found that the fracture mode transforms from ductile to brittle when the sample is annealed at a higher crystallization temperature, at which brittle intermetallic compounds appear.

  14. Glass-Forming Ability and Early Crystallization Kinetics of Novel Cu-Zr-Al-Co Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Xiaoliang Han

    2016-09-01

    Full Text Available In recent years, CuZr-based bulk metallic glass (BMG composites ductilized by a shape memory B2 CuZr phase have attracted great attention owing to their outstanding mechanical properties. However, the B2 CuZr phase for most CuZr-based glass-forming compositions is only stable at very high temperatures, leading to the uncontrollable formation of B2 crystals during quenching. In this work, by introducing Co (i.e., 4, 5, and 6 at. % and 10 at. % Al into CuZr-based alloys, the relatively good glass-forming ability (GFA of CuZr-based alloys still can be achieved. Meanwhile, the B2 phase can be successfully stabilized to lower temperatures than the final temperatures of crystallization upon heating CuZr-based BMGs. Unlike previous reported CuZr-based BMGs, the primary crystallization products upon heating are mainly B2 CuZr crystals but not CuZr2 and Cu10Zr7 crystals. Furthermore, the primary precipitates during solidification are still dominated by B2 crystals, whose percolation threshold is detected to lie between 10 ± 2 vol. % and 31 ± 2 vol. %. The crystallization kinetics underlying the precipitation of B2 crystals was also investigated. Our results show that the present glass-forming composites are promising candidates for the fabrication of ductile CuZr-based BMG composites.

  15. On the origin of bulk glass forming ability in Cu-Hf, Zr alloys

    Science.gov (United States)

    Ristić, Ramir; Zadro, Krešo; Pajić, Damir; Figueroa, Ignacio A.; Babić, Emil

    2016-04-01

    Understanding the formation of bulk metallic glasses (BMG) in metallic systems and finding a reliable criterion for selection of BMG compositions are among the most important issues in condensed-matter physics and material science. Using the results of magnetic susceptibility measurements performed on both amorphous and crystallized Cu-Hf alloys (30-70 at% Cu) we find a correlation between the difference in magnetic susceptibilities of corresponding glassy and crystalline alloys and the variation in the glass forming ability (GFA) in these alloys. Since the same correlation can be inferred from data for the properties associated with the electronic structure of Cu-Zr alloys, it seems quite general and may apply to other glassy alloys based on early and late transition metals. This correlation is plausible from the free-energy considerations and provides a simple way to select the compositions with high GFA.

  16. Ductile Bulk Aluminum-Based Alloy with Good Glass-Forming Ability and High Strength

    Institute of Scientific and Technical Information of China (English)

    ZHUO Long-Chao; PANG Shu-Jie; WANG Hui; ZHANG Tao

    2009-01-01

    Based on a new approach for designing glassy alloy compositions,bulk Al-based alloys with good glass-forming ability (GFA) are synthesized.The cast Al86Si0.5Ni4.06Co2.94 Y6Sc0.5 rod with a diameter of 1 mm shows almost fully amorphous structure besides about 5% fcc-Al nucleated in the center of the rod.The bulk alloy with high Al concentration exhibits an ultrahigh yield strength of 1.18 Gpa and maximum strength of 1.27 Gpa as well as an obvious plastic strain of about 2.4% during compressive deformation.This light Al-based alloy with good GFA and mechanical properties is promising as a new high specific strength material with good deformability.

  17. Soft-ferromagnetic bulk glassy alloys with large magnetostriction and high glass-forming ability

    Directory of Open Access Journals (Sweden)

    Jiawei Li

    2011-12-01

    Full Text Available The effect of Dy addition on the glass-forming ability (GFA, magnetostriction as well as soft-magnetic properties and fracture strength in FeDyBSiNb glassy alloys was investigated. In addition to the increase of supercooled liquid region from 55 to 100 K, the addition of Dy is effective in approaching alloy to an eutectic point and increasing the saturation magnetostrction (λs. Accordingly, bulk glassy alloy (BGA rods with diameters up to 4 mm were produced, which exhibit a large λs as high as 65×10-6. Besides, the BGA system exhibits superhigh fracture strength of 4000 MPa, combined with good soft-magnetic properties.

  18. Atomistic modelling and prediction of glass forming ability in bulk metallic glasses

    Science.gov (United States)

    Sedighi, Sina

    Atomistic modeling (via molecular dynamics with EAM interaction potentials) was conducted for the detailed investigation of kinetics, thermodynamics, structure, and bonding in Ni-Al and Cu-Zr metallic glasses. This work correlates GFA with the nature of atomic-level bonding and vibrational properties, with results potentially extensible to the Transition Metal -- Transition Metal and Transition Metal -- Metalloid alloy classes in general. As a first step in the development of a liquid-only GFA tuning approach, an automated tool has also been created for the broad compositional sampling of liquid and glassy phase properties in multicomponent (binary, ternary, quaternary) alloy systems. Its application to the Cu-Zr alloy system shows promising results, including the successful identification of the two highest GFA compositions, Cu50Zr50 and Cu64Zr 36. Combined, the findings of this work highlight the critical importance of incorporating more complex alloy-specific information regarding the nature of bonding and ordering at the atomic level into such an approach.

  19. Connection between the packing efficiency of binary hard spheres and the glass-forming ability of bulk metallic glasses

    Science.gov (United States)

    Zhang, Kai; Smith, W. Wendell; Wang, Minglei; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2014-09-01

    We perform molecular dynamics simulations to compress binary hard spheres into jammed packings as a function of the compression rate R, size ratio α, and number fraction xS of small particles to determine the connection between the glass-forming ability (GFA) and packing efficiency in bulk metallic glasses (BMGs). We define the GFA by measuring the critical compression rate Rc, below which jammed hard-sphere packings begin to form "random crystal" structures with defects. We find that for systems with α ≳0.8 that do not demix, Rc decreases strongly with ΔϕJ, as Rc˜exp(-1/ΔϕJ2), where ΔϕJ is the difference between the average packing fraction of the amorphous packings and random crystal structures at Rc. Systems with α ≲0.8 partially demix, which promotes crystallization, but we still find a strong correlation between Rc and ΔϕJ. We show that known metal-metal BMGs occur in the regions of the α and xS parameter space with the lowest values of Rc for binary hard spheres. Our results emphasize that maximizing GFA in binary systems involves two competing effects: minimizing α to increase packing efficiency, while maximizing α to prevent demixing.

  20. Connection between the packing efficiency of binary hard spheres and the glass-forming ability of bulk metallic glasses.

    Science.gov (United States)

    Zhang, Kai; Smith, W Wendell; Wang, Minglei; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2014-09-01

    We perform molecular dynamics simulations to compress binary hard spheres into jammed packings as a function of the compression rate R, size ratio α, and number fraction x(S) of small particles to determine the connection between the glass-forming ability (GFA) and packing efficiency in bulk metallic glasses (BMGs). We define the GFA by measuring the critical compression rate R(c), below which jammed hard-sphere packings begin to form "random crystal" structures with defects. We find that for systems with α≳0.8 that do not demix, R(c) decreases strongly with Δϕ(J), as R(c)∼exp(-1/Δϕ(J)(2)), where Δϕ(J) is the difference between the average packing fraction of the amorphous packings and random crystal structures at R(c). Systems with α≲0.8 partially demix, which promotes crystallization, but we still find a strong correlation between R(c) and Δϕ(J). We show that known metal-metal BMGs occur in the regions of the α and x(S) parameter space with the lowest values of R(c) for binary hard spheres. Our results emphasize that maximizing GFA in binary systems involves two competing effects: minimizing α to increase packing efficiency, while maximizing α to prevent demixing.

  1. Enhancement of glass-forming ability of Fe-based bulk metallic glasses with high saturation magnetic flux density

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    Mingxiao Zhang

    2012-06-01

    Full Text Available The effects of substituting Fe with Ni on thermal properties, glass-forming ability (GFA and magnetic properties of Fe76-xNixMo3.5P10C4B4Si2.5 (x = 0−30 at.% alloys were investigated in detail. The breadth of the supercooled liquid region was found to gradually increase from 42 to 55 K with increasing Ni content to 30 at.%. When x = 5 at.%, the alloy composition approached a eutectic point, resulting in an increase in GFA. As a result, FeNiMoPCBSi bulk metallic glasses with critical diameters up to 5.5 mm were successfully synthesized by copper mold casting. These glassy alloys exhibit a high saturation magnetic flux density of 0.75−1.21 T and excellent soft magnetic properties, i.e., low coercive force of 1.1−2.0 A/m, and high effective permeability of 14400−19700 at 1 kHz under a field of 1 A/m. The reasons for the high stability of the supercooled liquid, and the high GFA as well as excellent soft magnetic properties are discussed in this article.

  2. Wetting of bulk metallic glass forming liquids on metals and ceramics

    Science.gov (United States)

    Ding, Shiyan; Kong, Jian; Schroers, Jan

    2011-08-01

    Contact wetting angle of Pd43Ni10Cu27P20, Pt57.5Cu14.7Ni5.3P22.5, Au49Ag5.5Pd2.3Cu26.9Si16.3, and Zr57Nb5Cu15.4Ni12.6Al10 bulk metallic glass forming alloys have been determined on materials that are used in micro and nano fabrication. Employing the sessile drop technique at a temperature above the corresponding melting temperatures, three kinds of wetting behaviors are observed, spanning from θ ≈ 140°, over neutral wetting, θ ≈ 80°, to almost complete wetting, θ < 5°. The origin for complete wetting is the formation of an interface phase promoting wetting. Estimations of the contact wetting angles are presented for temperatures in the supercooled liquid region where micro and nano fabrication is typically carried out. Consequences of the observed wetting behaviors for nanoforming are discussed.

  3. AC Calorimetry and Thermophysical Properties of Bulk Glass-Forming Metallic Liquids

    Science.gov (United States)

    Johnson, William L.

    2000-01-01

    Thermo-physical properties of two bulk metallic glass forming alloys, Ti34Zr11Cu47Ni8 (VIT 101) and Zr57Nb5Ni12.6Al10CU15.4 (VIT 106), were investigated in the stable and undercooled melt. Our investigation focused on measurements of the specific heat in the stable and undercooled liquid using the method of AC modulation calorimetry. The VIT 106 exhibited a maximum undercooling of 140 K in free radiative cooling. Specific heat measurements could be performed in stable melt down to an undercooling of 80 K. Analysis of the specific heat data indicate an anomaly near the equilibrium liquidus temperature. This anomaly is also observed in y the temperature dependencies of the external relaxation time, the specific volume, and the surface tension; it is tentatively attributed to a phase separation in the liquid state. The VIT 101 specimen exhibited a small undercooling of about 50 K. Specific heat measurements were performed in the stable and undercooled melt. These various results will be combined with ground based work such as the measurement of T-T-T curves in the electrostatic levitator and low temperature viscosity and specific heat measurements for modeling the nucleation kinetics of these alloys.

  4. Molecular dynamics study of the ternary Cu50Ti25Zr25 bulk glass forming alloy

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    Celtek M.

    2011-05-01

    Full Text Available The structure and thermodynamic properties of a ternary Cu50Ti25Zr25 metallic glass forming alloy in solid-liquid to glass phases were studied using molecular dynamics (MD method based on tight-binding (TB potentials. An atomic description of the melting, glass formation and crystallization process has been analyzed using different heating and cooling rates. The computed Glass Forming Ability (GFA parameters are in good agreement with experimental data. The structure analysis of the Cu50Ti25Zr25 based on molecular dynamics simulation will be also presented and compared with available MD results. We have also discussed the crystallization transition with two different interatomic potentials used in this work

  5. Improvement of corrosion resistance in NaOH solution and glass forming ability of as-cast Mg-based bulk metallic glasses by microalloying

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    Peng Hao

    2011-02-01

    Full Text Available The influences of the addition of Ag on the glass forming ability (GFA and corrosion behavior were investigated in the Mg-Ni-based alloy system by X-ray diffraction (XRD and electrochemical polarization in 0.1 mol/L NaOH solution. Results shows that the GFA of the Mg-Ni-based BMGs can be improved dramatically by the addition of an appropriate amount of Ag; and the addition element Ag can improve the corrosion resistance of Mg-Ni-based bulk metallic glass. The large difference in atomic size and large negative mixing enthalpy in alloy system can contribute to the high GFA. The addition element Ag improves the forming speed and the stability of the passive film, which is helpful to decrease the passivation current density and to improve the corrosion resistance of Mg-Ni-based bulk metallic glass.

  6. Liquid -to-glass transition in bulk glass-forming Cu55-xZr45Agx alloys using molecular dynamic simulations

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    Celtek M.

    2011-05-01

    Full Text Available We report results from molecular dynamics (MD studies concerning the microscopic structure of the ternary, bulk metallic glass-forming Cu55-x Zr45Agx (x=0,10,20 alloys using tight-binding potentials. Understanding of the nature of Glass Forming Ability (GFA of studied alloys, GFA parameters, glass transition temperature (T-g, melting temperature (T-m, reduced glass transition temperature (T-g/T-m, the supercooled liquid region and other parameters were simulated and compared with experiments. The computed pair distribution functions reproduce well experimental x-ray data of Inoue and co-workers. Structure analysis of the Cu-Zr-Ag alloy based on MD simulation will be also presented

  7. Viscosity properties and strong liquid behavior of Pr60Ni25Al15 bulk metallic glass-forming liquids

    Institute of Scientific and Technical Information of China (English)

    WANG Dan; ZHANG Di; WANG ShuYing; NING QianYan; ZHENG CaiPing; YAN Yuan; LIU Jia; SUN MinHua

    2008-01-01

    Pr60Ni25Al15 bulk metallic glass in a cuboid form with dimensions of 2 mm×2 mm×55 mm by copper mold casting method was cast.The dynamic viscosity near the glass transition region for Pr60Ni25Al15 was measured by three-point beam bending methods.The fragility parameter m and activation energy for viscous flow of the liquid sample were calculated to be: m = 31.66, E= 10689.17 K, respectively.It was shown that the supercooled liquid of Pr60Ni25Al15 alloy behaved much closer to strong glasses.The variation of active energy with temperature in supercooled liquid was analyzed.It was found that Kivelson's super-Arrhenius equation is not suitable for description of the activation energy in a supercooled region of Bulk metallic glass, and there is a direct proportion between activation energy crystal-lization and activation energy of viscous flow.

  8. Viscosity properties and strong liquid behavior of Pr60Ni25Al15 bulk metallic glass-forming liquids

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Pr60Ni25Al15 bulk metallic glass in a cuboid form with dimensions of 2 mm×2 mm×55 mm by copper mold casting method was cast. The dynamic viscosity near the glass transition region for Pr60Ni25Al15 was measured by three-point beam bending methods. The fragility parameter m and activation energy for viscous flow of the liquid sample were calculated to be:m=31.66,E=10689.17 K,respectively. It was shown that the supercooled liquid of Pr60Ni25Al15 alloy behaved much closer to strong glasses. The variation of active energy with temperature in supercooled liquid was analyzed. It was found that Kivelson’s super-Arrhenius equation is not suitable for description of the activation energy in a supercooled region of Bulk metallic glass,and there is a direct proportion between activation energy crystal-lization and activation energy of viscous flow.

  9. Co-based soft magnetic bulk glassy alloys optimized for glass-forming ability and plasticity

    Indian Academy of Sciences (India)

    LI LI; HUAIJUN SUN; YUNZHANG FANG; JIANLONG ZHENG

    2016-06-01

    Co-based bulk glassy alloys (BGAs) have become more and more important because of their nearly zero magnetostriction and high giant magneto-impedance effect. Here, we report the improvement of glass-formingability (GFA), soft-magnetic properties and plasticity by a small addition of Mo atoms in CoFeBSiNbMo BGAs.(Co$_{0.6}$Fe$_{0.4}$)$_{69}$B$_{20.8}$Si$_{5.2}$Nb$_{5−x}$Mo$_{x}$ ferromagnetic BGA cylindrical glassy rods were fabricated successfully with adiameter of 5 mm by conventional copper mould casting method. It reveals that the substitution of a small amount of Mo for Nb makes the composition to approach a eutectic point and effectively enhances the GFA of alloy. Inaddition to high GFA and superhigh strength, the compressive test shows that the Mo addition can improve the plasticity for the obtained BGAs. The combination of high GFA, excellent soft-magnetic properties and good plasticitydemonstrated in our alloys is promising for the future applications as functional materials.

  10. Effect of Yttrium Addition on Glass-Forming Ability and Magnetic Properties of Fe–Co–B–Si–Nb Bulk Metallic Glass

    Directory of Open Access Journals (Sweden)

    Teruo Bitoh

    2015-06-01

    Full Text Available The glass-forming ability (GFA and the magnetic properties of the [(Fe0.5Co0.50.75B0.20Si0.05]96Nb4−xYx bulk metallic glasses (BMGs have been studied. The partial replacement of Nb by Y improves the thermal stability of the glass against crystallization. The saturation mass magnetization (σs exhibits a maximum around 2 at. % Y, and the value of σs of the alloy with 2 at. % Y is 6.5% larger than that of the Y-free alloy. The coercivity shows a tendency to decrease with increasing Y content. These results indicate that the partial replacement of Nb by Y in the Fe–Co–B–Si–Nb BMGs is useful to simultaneous achievement of high GFA, high σs, and good soft magnetic properties.

  11. The Effect of Iron Content on Glass Forming Ability and Thermal Stability of Co–Fe–Ni–Ta–Nb–B–Si Bulk Metallic Glass

    Directory of Open Access Journals (Sweden)

    Aytekin Hitit

    2016-12-01

    Full Text Available In this study, change in glass forming ability (GFA and thermal stability of Co–Fe-based bulk metallic glasses were investigated as a function of iron content. Cylindrical samples of alloys with diameters of up to 4 mm were synthesized by a suction casting method in an arc furnace. Structures and thermal properties of the as-cast samples were determined by X-ray diffraction (XRD and differential scanning calorimetry (DSC, respectively. It was found that the critical casting thickness of the alloys reduced as iron content was increased and cobalt content was decreased. It was determined that GFA parameters, reduced glass transition temperature (Tg/Tl and δ (= Tx/(Tl − Tg, show a very good correlation with critical casting thickness values. It was also observed that changing iron content did not effect thermal properties of the alloys.

  12. Preparation and characterization of Fe-based bulk metallic glasses in plate form

    Energy Technology Data Exchange (ETDEWEB)

    Lavorato, G.C. [INTECIN (FIUBA-CONICET), Paseo Colon 850, Capital Federal (Argentina); Dipartimento di Chimica IFM and NIS, Universita di Torino, Torino (Italy); Fiore, G.; Castellero, A.; Baricco, M. [Dipartimento di Chimica IFM and NIS, Universita di Torino, Torino (Italy); Moya, J.A., E-mail: jmoya.fi.uba@gmail.com [IESIING, Facultad de Ingenieria e Informatica, UCASAL, Salta (Argentina); CONICET (Argentina)

    2012-08-15

    Amorphous alloys with composition (at%) Fe{sub 48}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Gd{sub 2} (alloy A) and Fe{sub 48}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Y{sub 2} (alloy B) were prepared either using pure elements (A and B1) and a commercial AISI430 steel as a base material (B2). When prepared from pure elements both alloys (A and B1) could be cast in plate form with a fixed thickness of 2 mm and variable lengths between 10 and 20 mm by means of copper-mold injection in air atmosphere. In the case of alloy B2, prepared using commercial grade raw materials, rods of 2 mm diameter were obtained. X-ray diffraction and scanning electron microscopy observations confirmed that an amorphous structure was obtained in all the as-cast samples. A minor fraction of crystalline phases (oxides and carbides) was detected on the as-cast surface. Differential scanning calorimetry measurements showed a glass transition temperature at 856 K for alloy A and 841 K for alloy B1, and an onset crystallization temperature of 887 K for alloy A and 885 K for alloy B1. In the case of alloy B2 a slightly different crystallization sequence was observed. Values of hardness ({approx}13 GPa) and the Young modulus ({approx}180 GPa) were measured by nanoindentation for both the alloys. The effects of adverse casting conditions (such as air atmosphere, non-conventional injection copper mold casting and partial replacement of pure elements with commercial grade raw materials) on the glass formation and properties of the alloy are discussed.

  13. Isoconfigurational elastic constants and liquid fragility of a bulk metallic glass forming alloy.

    Science.gov (United States)

    Lind, Mary Laura; Duan, Gang; Johnson, William L

    2006-07-07

    Samples of Zr(46.25)Ti(8.25)Cu(7.5)Ni(10)Be(27.5) were isothermally annealed and quenched near the glass transition temperature and studied by the pulse-echo overlap technique. The shear modulus G of the samples shows a strong reversible dependence on annealing temperatures and, thus, on the specific configurational potential energy of the equilibrium liquid. The low-T dependence of G of the configurationally frozen glasses shows linear temperature dependence as expected by Debye-Grüneisen theory. The T dependence of G in the liquid state is directly related to the viscosity and fragility of the liquid.

  14. A Combinatorial Approach to the Investigation of Metal Systems that Form Both Bulk Metallic Glasses and High Entropy Alloys

    Science.gov (United States)

    Welk, Brian A.; Gibson, Mark A.; Fraser, Hamish L.

    2016-03-01

    In this work, compositionally graded specimens were deposited using the laser engineered net-shaping (LENS™) additive manufacturing technique to study the glass-forming ability of two bulk metallic glass (BMG) and high entropy alloy (HEA) composite systems. The first graded specimen varied from Zr57Ti5Al10Cu20Ni8 (BMG) to CoCrFeNiCu0.5 (HEA) and the second graded specimen varied from TiZrCuNb (BMG) to (TiZrCuNb)65Ni35 (HEA). After deposition, laser surface melting experiments were performed parallel to the gradient to remelt and rapidly solidify the specimen. Scanning electron microscopy and energy dispersive x-ray spectroscopy were used to determine the morphology and composition variations in the as-deposited and laser surface melted phases. Selected area diffraction of the melt pool regions confirmed an almost fully amorphous region in the first gradient and an amorphous matrix/crystalline dendrite composite structure in the second gradient.

  15. Toughness of Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Shantanu V. Madge

    2015-07-01

    Full Text Available Bulk metallic glasses (BMGs have desirable properties like high strength and low modulus, but their toughness can show much variation, depending on the kind of test as well as alloy chemistry. This article reviews the type of toughness tests commonly performed and the factors influencing the data obtained. It appears that even the less-tough metallic glasses are tougher than oxide glasses. The current theories describing the links between toughness and material parameters, including elastic constants and alloy chemistry (ordering in the glass, are discussed. Based on the current literature, a few important issues for further work are identified.

  16. Crystalline Precipitate in a Bulk Glass Forming Zr-Based Alloy and Its Effect on Mechanical Properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Cylindrical and sheet samples of bulk metallic glass with a nominal composition of Zr52.5Ni14.6Al10Cu17.9Ti5 (at. pct) were prepared by melt injection casting. The crystalline precipitates formed during the casting were studied by metallographic observations and selected-area electron diffractions. The effect of crystalline precipitates on the mechanical properties were investigated by tensile and compressive tests at room temperature. Oxygen contents and the sample sizes (or cooling rates) strongly affect the formation of the crystalline precipitates. Overheating the alloy melt up to 200 K above its melting temperature can effectively prevent the formation of the crystalline precipitates to get fully glass samples with diameters up to 2 mm for cylinders and thickness up to 1 mm for sheets even the oxygen content is as higher as 0.08 wt pct.With increasing the sample sizes, the crystalline precipitates increase in volume fraction and size. The formation of the precipitates experienced two stages, i.e., initially nucleation and isotropic growth, and then anisotropic growth, finally forming faceted morphologies. Fully glassy Zr52.5Ni14.6Al10Cu17.9Ti5 alloy exhibits excellent tensile and compressive properties at room temperature. The presence of crystalline precipitates significantly decreases the tensile and compressive properties. With increasing the crystalline precipitates, the area of vein patterns on the fracture surface decreases, but the fracture steps increase, and the fracture mode changes from ductile to brittle resulting from the larger stress concentration caused by the larger sizes and faceted shapes of the crystalline precipitates.

  17. Chemical short-range order domain in bulk amorphous alloy and the prediction of glass forming ability

    Institute of Scientific and Technical Information of China (English)

    HUI; Xidong(惠希东); YAO; Kefu(姚可夫); KOU; Hongchao(寇宏超); CHEN; Guoliang(陈国良)

    2003-01-01

    Short-range order domains of face central cubic Zr2Ni (F-Zr2Ni) and tetragonal Zr2Ni (T-Zr2Ni) type structure with a size about 1-3 nanometers were observed in bulk amorphous Zr52.5Cu17.9Ni14.6Al10Ti5 alloy by using HREM and nano-beam electron diffraction technique. A new thermodynamic model was formulated based on the concept of chemical short-range order (SCRO). The molar fractions of CSRO and thermodynamic properties in Ni-Zr, Cu-Zr, Al-Zr, Al-Ni, Zr-Ni-Al and Zr-Ni-Cu were calculated. According to the principle of maximum the optimum glass forming ability (GFA) compositions were predicted in binary and ternary alloys. These results were proved to be valid by the experimental data of crystallizing activation energy, ΔTx and XRD patterns. The TTT curves of Zr-Ni-Cu alloys calculated based on CSRO model shows that the lowest critical cooling rate GFA is in the order of 100 K/s, which is close to the practical cooling rate for the preparation of Zr-based BMG alloys.

  18. Binary Cu-Zr Bulk Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    TANG Mei-Bo; ZHAO De-Qian; PAN Ming-Xiang; WANG Wei-Hua

    2004-01-01

    @@ We report that bulk metallic glasses (BMGs) can be produced up to 2 mm by a copper mould casting in Cux Zr1-x binary alloy with a wide glass forming composition range (45 < x < 60 at.%). We find that the formation mechanism for the binary Cu-Zr binary BMG-forming alloy is obviously different from that of the intensively studied multicomponent BMGs. Our results demonstrate that the criteria for the multicomponent alloys with composition near deep eutectic and strong liquid behaviour are no longer the major concern for designing BMGs.

  19. Effect of Hafnium and Zirconium to Glass Forming Ability, Thermal Stability, Plasticity Deformation and Crystallization of Ni-Free Pentabasic Ti-Based Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Oak J.J.

    2017-06-01

    Full Text Available The newly designed Ti-based bulk metallic glass (BMG in which case of fracture behavior was observed 1990MPa to compressive strength with a wide plastic deformation around 7% after process of elastic deformation. This phenomenon can be compared with those of Ti-based alloys and other Ti-based BMGs and indicates high potential to be applied in use. It was evaluated the Ti-based BMG for thermal stability that the reduced glass parameters, ΔTx, Trg and γ, are 79K, 0.50 and 0.38, respectively. In addition, it reveals high activation energies for crystallization in which are estimated to Ex1 = 291.77 ±9.71 kJ/mol, Ex2 = 588.77 ±28.88 kJ/mol and Ex3 = 330.26 ±3.61 kJ/mol on kissinger plotting in this study.

  20. Gibbs Free Energy and Activation Energy of ZrTiAlNiCuSn Bulk Glass Forming Alloys

    Institute of Scientific and Technical Information of China (English)

    Jianfei SUN; Jun SHEN; Zhenye ZHU; Gang WANG; Dawei XING; Yulai GAO; Bide ZHOU

    2004-01-01

    The Gibbs free energy differences between the supercooled liquid and the crystalline mixture for the (Zr52.5Ti5Al10- Ni14.6Cu17.9)(100-x)/100Snx ·(x=0, 1, 2, 3, 4 and 5) glass forming alloys are estimated by introducing the equation proposed by Thompson, Spaepen and Turnbull. It can be seen that the Gibbs free energy differences decrease first as the increases of Sn addition smaller than 3, then followed by a decrease due to the successive addition of Sn larger than 3, indicating that the thermal stabilities of these glass forming alloys increase first and then followed by a decrease owing to the excessive addition of Sn. Furthermore, the activation energy of Zr52.5Ti5Al10Ni14.6Cu17.9 and (Zr5 2.5Ti5 Al10 Ni14.6 Cu 17.9)0.97Sn3 was evaluated by Kissinger equation. It is noted that the Sn addition increases the activation energies for glass transition and crystallization, implying that the higher thermal stability can be obtained by appropriate addition of Sn.

  1. Effects of Mo additions on the glass-forming ability and magnetic properties of bulk amorphous Fe-C-Si-B-P-Mo alloys

    Institute of Scientific and Technical Information of China (English)

    YI; Seonghoon

    2010-01-01

    Glass formation, mechanical and magnetic properties of the Fe76-xC7.0Si3.3B5.0P8.7Mox (x=0, 1 at.%, 3 at.% and 5 at.%) alloys prepared using an industrial Fe-P master alloy have been studied. With the substitution of Mo for Fe, glass-forming ability (GFA) was significantly enhanced and fully amorphous rods with a diameter of up to 5 mm were produced in the alloy with 3% Mo. The Mo-containing amorphous alloys also exhibited high fracture strength of 3635–3881 MPa and excellent magnetic properties including a high saturation magnetization of 1.10–1.41 T, a high Curie temperature and a low coercive force. The unique combination of high GFA, high fracture strength and excellent magnetic properties make the newly developed bulk metallic glasses viable for practical engineering applications.

  2. Bulk metallic glasses: A new class of engineering materials

    Indian Academy of Sciences (India)

    Joysurya Basu; S Ranganathan

    2003-06-01

    Bulk glass-forming alloys have emerged over the past fifteen years with attractive properties and technological promise. A number of alloy systems based on lanthanum, magnesium, zirconium, palladium, iron, cobalt and nickel have been discovered. Glass-forming ability depends on various factors like enthalpy of mixing, atomic size and multicomponent alloying. A number of processes is available to synthesise bulk metallic glasses. The crystallisation behaviour and mechanical properties of these alloys pose interesting scientific questions. Upon crystallisation many of these glasses transform to bulk nanocrystals and nanoquasicrystals. A detailed study of the structure and the crystallisation behaviour of glasses has enabled the elucidation of the possible atomic configuration in liquid alloys. Their crystallisation behaviour can be exploited to synthesise novel nanocomposite microstructures and their mechanical properties can be enhanced. A broad overview of the present status of the science and technology of bulk metallic glasses and their potential technological uses is presented.

  3. Enhanced plasticity of Zr-based bulk metallic glass composite by in situ formed β-Zr dendritics

    Institute of Scientific and Technical Information of China (English)

    SUN Guoyuan; CHEN Guang; CHEN Guoliang

    2007-01-01

    A Zr56.2Ti13.8Nb5.0Cu6.9Ni5.6Be12.5 bulk metallic glasscomposite with enhanced plasticity by in situ formed bcc β-Zr solid solution was prepared by water quenching.The ductile βphase with a volume fraction of about 30% possesses a developed dendritic morphology.The composite exhibits a pure plastic strain of 10.2% combined with a large elastic strain limit of 2% and a high ultimate strength of 1778 Mpa upon room-temperature compression.Microscopic observa- tion shows numbers of wave-like shear bands distributed on the surface of the compressive samples.

  4. Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses

    Science.gov (United States)

    Zhang, Kai; Fan, Meng; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2015-11-01

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate Rc, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. Rc (or the corresponding critical casting thickness dc) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small Rc alloys are typically poor glass-formers with large Rc > 1010 K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with Rc approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for designing BMGs with cm or greater casting thickness.

  5. Effect of vanadium substitution for zirconium on the glass forming ability and mechanical properties of a Zr{sub 65}Cu{sub 17.5}Ni{sub 10}Al{sub 7.5} bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Khademian, Nima, E-mail: nkhademian@gmail.com [Department of Mechanics, Islamshahr Branch, Islamic Azad University (IAU), Tehran (Iran, Islamic Republic of); Gholamipour, Reza [Iranian Research Organization for Science and Technology (IROST), Tehran (Iran, Islamic Republic of); Shahri, Farzad; Tamizifar, Morteza [Faculty of Engineering and High-Tech., Iran University of Industries and Mines (IUIM), Tehran (Iran, Islamic Republic of)

    2013-01-05

    Highlights: Black-Right-Pointing-Pointer The addition of V is effective for a decrease in GFA of Zr-based BMGs. Black-Right-Pointing-Pointer Mechanical properties of Zr-based BMGs are enhanced largely due to V addition. Black-Right-Pointing-Pointer Correlations among the elastic moduli, fracture strength, Vicker's hardness and glass transition for Zr-based BMGs. Black-Right-Pointing-Pointer Critical resolved shear stress ({tau}) of the Zr{sub 65-x}Cu{sub 17.5}Ni{sub 10}Al{sub 7.5}V{sub x} alloys decreases with the increase of V content. - Abstract: Effect of vanadium on the thermal and mechanical properties of the Zr{sub 65}Cu{sub 17.5}Ni{sub 10}Al{sub 7.5} bulk metallic glass has been studied. The vanadium substitution for zirconium in the bulk metallic glass leads to the decrease of the glass forming ability in constant cooling rate; as well as co-precipitation of Zr{sub 2}Ni and Zr{sub 2}Cu crystalline phases in amorphous matrix. The size of the crystallites are about 20-50 nm in amorphous matrix and they act as a barrier against of rapid propagation of shear bands. In fact, the nanocrystalline phases in amorphous matrix cause the increase of the strain and the quasi-static compression strength about 58% and 20%, respectively.

  6. Making bulk-conductive glass microchannel plates

    Science.gov (United States)

    Yi, Jay J. L.; Niu, Lihong

    2008-02-01

    The fabrication of microchannel plate (MCP) with bulk-conductive characteristics has been studied. Semiconducting clad glass and leachable core glass were used for drawing fibers and making MCP. Co-axial single fiber was drawn from a platinum double-crucible in an automatic fiberizing system, and the fibers were stacked and redrawn into multifiber by a special gripping mechanism. The multifibers were stacked again and the boule was made and sliced into discs. New MCPs were made after chemically leaching process without the traditional hydrogen firing. It was shown that bulk-conductive glass MCP can operate at higher voltage with lower noise.

  7. "Work-Hardenable" ductile bulk metallic glass.

    Science.gov (United States)

    Das, Jayanta; Tang, Mei Bo; Kim, Ki Buem; Theissmann, Ralf; Baier, Falko; Wang, Wei Hua; Eckert, Jürgen

    2005-05-27

    Usually, monolithic bulk metallic glasses undergo inhomogeneous plastic deformation and exhibit poor ductility (< 1%) at room temperature. We present a new class of bulk metallic glass, which exhibits high strength of up to 2265 MPa together with extensive "work hardening" and large ductility of 18%. Significant increase in the flow stress was observed during deformation. The "work-hardening" capability and ductility of this class of metallic glass is attributed to a unique structure correlated with atomic-scale inhomogeneity, leading to an inherent capability of extensive shear band formation, interactions, and multiplication of shear bands.

  8. Glass Formation Ability and Kinetics of the Gd55Al20Ni25 Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    JO Chol-Lyong; XIA Lei; DING Ding; DONG Yuan-Da

    2006-01-01

    @@ We report a new bulk glass-forming alloy Gd55Al20Ni25. The bulk sample of the alloy is prepared in the shape of rods in diameter 2mm by suction casting. The rod exhibits typical amorphous characteristics in the xray diffraction pattern, paramagnetic property at 300K, distinct glass transition and multi-step crystallization behaviour in differential scanning calorimetry traces. The glass formation ability of the alloy is investigated by using the reduced glass transition temperature Tγg and the parameter γ. Kinetics of glass transition and primary crystallization is also studied. The fragility parameter m obtained from the Vogel-Fulcher-Tammann dependence of glass transition temperature Tg on ln φ (φ is the heating rate) classifies the bulk metallic glasses into the intermediate category according to Angells classification.

  9. Criticality in Bulk Metallic Glass Constituent Elements

    Science.gov (United States)

    Mota, Rodrigo Miguel Ojeda; Graedel, T. E.; Pekarskaya, Evgenia; Schroers, Jan

    2017-07-01

    Bulk metallic glasses (BMGs), which readily form amorphous phases during solidification, are increasingly being used in first applications of watch components, electronic casings, and sporting goods. The compositions of BMGs typically include four to six elements. Various political and geological factors have recently led to supply disruptions for several metals, including some present in BMG compositions. In this work, we assess the "criticality" of 22 technologically interesting BMG compositions, compare the results with those for three common engineering alloy groups, and derive recommendations for BMG composition choices from a criticality perspective. The criticality of BMGs is found to be generally much higher compared with those for the established engineering alloys. Therefore, criticality concerns should also be considered in the choice between existing and developing novel BMGs.

  10. Modeling of Microimprinting of Bulk Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    Ming CHENG; John A. Wert

    2006-01-01

    A finite element analysis (FEA) model has been developed to analyze microimprinting of bulk metallic glasses (BMG) near the glass transition temperature (Tg). The results reveal an approximately universal imprinting response for BMG, independent of surface feature length scale. The scale-independent nature of BMG imprinting derives from the flow characteristics of BMG in the temperature range above Tg. It also shows that the lubrication condition has a mild influence on BMG imprinting in the temperature range above Tg.

  11. Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai; Fan, Meng; Liu, Yanhui; Schroers, Jan [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Shattuck, Mark D. [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Department of Physics and Benjamin Levich Institute, The City College of the City University of New York, New York, New York 10031 (United States); O’Hern, Corey S. [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States)

    2015-11-14

    When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate R{sub c}, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. R{sub c} (or the corresponding critical casting thickness d{sub c}) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small R{sub c} < 10{sup −2} K/s, pure metals and most alloys are typically poor glass-formers with large R{sub c} > 10{sup 10} K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with R{sub c} approaching that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important for

  12. Responses of bone-forming cells on pre-immersed Zr-based bulk metallic glasses: Effects of composition and roughness.

    Science.gov (United States)

    Huang, L; Cao, Z; Meyer, H M; Liaw, P K; Garlea, E; Dunlap, J R; Zhang, T; He, W

    2011-01-01

    Bulk metallic glasses (BMGs) demonstrate attractive properties for potential biomedical applications, owing to their amorphous structure. The present work has investigated the biocompatibility of Zr-based BMGs by studying the cellular behavior of bone-forming mouse MC3T3-E1 pre-osteoblast cells. A Ti-6Al-4V alloy was used as a reference material. Pre-immersion treatment was performed on BMG samples in phosphate-buffered saline prior to cell experiments. The effects of 1at.% yttrium alloying and surface roughness on cellular behavior were examined. The general biosafety of Zr-based BMGs for MC3T3-E1 cells was revealed as normal cell responses. Pre-immersion treatment was found to effectively reduce the surface concentrations of alloying elements. Micro-alloying with 1 at.% yttrium did not significantly affect cell adhesion and proliferation, but slightly decreased alkaline phosphatase (ALP) activity on rough surfaces. Lower cell adhesion and proliferation were found on smooth surfaces of Zr-based BMGs compared to their rougher counterparts. Higher ALP activity was detected on rougher surfaces. To obtain a mechanistic understanding surface free energy was correlated with cell adhesion. Copyright © 2010 Acta Materialia Inc. All rights reserved.

  13. Mechanical spectra of glass-forming liquids. I. Low-frequency bulk and shear moduli of DC704 and 5-PPE measured by piezoceramic transducers

    DEFF Research Database (Denmark)

    Hecksher, Tina; Olsen, Niels Boye; Nelson, Keith Adam

    2013-01-01

    We present dynamic shear and bulk modulus measurements of supercooled tetraphenyl-tetramethyl-trisiloxane (DC704) and 5-phenyl-4-ether over a range of temperatures close to their glass transition. The data are analyzed and compared in terms of time-temperature superposition (TTS), the relaxation...... time, and the spectral shape parameters. We conclude that TTS is obeyed to a good approximation for both the bulk and shear moduli. The loss-peak shapes are nearly identical, while the shear modulus relaxes faster than the bulk modulus. The temperature dependence of this decoupling of time scales...... is constant over the temperature range explored here. In addition, we demonstrate how one can measure reliably the DC shear viscosity over ten orders of magnitude by using the two measuring techniques in combination....

  14. Design of Cu8Zr5-based bulk metallic glasses

    Science.gov (United States)

    Yang, L.; Xia, J. H.; Wang, Q.; Dong, C.; Chen, L. Y.; Ou, X.; Liu, J. F.; Jiang, J. Z.; Klementiev, K.; Saksl, K.; Franz, H.; Schneider, J. R.; Gerward, L.

    2006-06-01

    Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu-Zr binary system, where we have demonstrated the existence of Cu8Zr5 icosahedral clusters in Cu61.8Zr38.2, Cu64Zr36, and Cu64.5Zr35.5 amorphous alloys. Furthermore, ternary bulk metallic glasses can be developed by doping the basic Cu-Zr alloy with a minority element. This hypothesis was confirmed in systems (Cu0.618Zr0.382)100-xNbx, where x =1.5 and 2.5at.%, and (Cu0.618Zr0.382)98Sn2. The present results may open a route to prepare amorphous alloys with improved glass forming ability.

  15. Design of Cu8Zr5-based bulk metallic glasses

    DEFF Research Database (Denmark)

    Yang, L.; Xia, J.H.; Wang, Q.;

    2006-01-01

    Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu-Zr binary syste.......382)(100-x)Nb-x, where x=1.5 and 2.5 at. %, and (Cu0.618Zr0.382)(98)Sn-2. The present results may open a route to prepare amorphous alloys with improved glass forming ability....

  16. Fe60CoxZr10Mo5W2B23-x(x=1,3,5,7,9)块状金属玻璃的非晶形成能力%Glass forming ability of Fe60 Cox Zr10Mo5 W2B23-x (x = 1,3,5,7,9) bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    刘冬艳; 张海峰; 邓胜涛; 胡壮麒

    2005-01-01

    The bulk Fe60CoxZr10Mo5W2B23-x (x= 1, 3, 5, 7, 9) amorphous rods with diameters of1.5 mm were successfully prepared by copper mold casting method with the low purity raw materials.The amorphous and crystalline states, and thermal parameters, such as the glass transition temperature (Tg), the initial crystallization temperature (Tx), the supercooled liquid region (ΔTx = TxTg), the reduced glass transition temperature Trg (Tg/Tm, Tm: the onset temperature of melting of the alloy, and Tg/T1, T1 : the finished temperature of melting of the alloy) were investigated by X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) analysis. Glass forming ability of Fe60CoxZr10Mo5W2B23-x (x=1, 3, 5, 7, 9)bulk metallic glasses has been studied. According to the results, the alloy (x=7) with the highest Trg (Tg/T1 =0. 607, Tg/T1 =0.590) value, has the strongest glass forming ability among these alloys because its composition is near eutectic composition.The wide supercooled liquid region over 72 K indicates the high thermal stability for this alloy system.This bulk metallic glass exhibits quite high strength (Hv 1020). The success of production of the Febased bulk metallic glass with industrial materials is of great significance for the future progress of basic research and practical application.

  17. Fabrication of Porous Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    Keqiang QIU; Yinglei REN

    2005-01-01

    An open-cell porous bulk metallic glass (BMG)with a diameter of at least 6 mm was fabricated by using an U-turn quartz tube and infiltration casting aroundsoluble NaCl placeholders. The pore formation and glassy structure were examined by optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the pores or cells are connected to each other and the specimenis composed of a mostly glassy phase.This paper provides a suitable method for fabrication of porous BMG and BMG with larger size in diameter.

  18. New Class of Plastic Bulk Metallic Glass

    Science.gov (United States)

    Chen, L. Y.; Fu, Z. D.; Zhang, G. Q.; Hao, X. P.; Jiang, Q. K.; Wang, X. D.; Cao, Q. P.; Franz, H.; Liu, Y. G.; Xie, H. S.; Zhang, S. L.; Wang, B. Y.; Zeng, Y. W.; Jiang, J. Z.

    2008-02-01

    An intrinsic plastic Cu45Zr46Al7Ti2 bulk metallic glass (BMG) with high strength and superior compressive plastic strain of up to 32.5% was successfully fabricated by copper mold casting. The superior compressive plastic strain was attributed to a large amount of randomly distributed free volume induced by Ti minor alloying, which results in extensive shear band formation, branching, interaction and self-healing of minor cracks. The mechanism of plasticity presented here suggests that the creation of a large amount of free volume in BMGs by minor alloying or other methods might be a promising new way to enhance the plasticity of BMGs.

  19. Drastic influence of minor Fe or Co additions on the glass forming ability, martensitic transformations and mechanical properties of shape memory Zr-Cu-Al bulk metallic glass composites.

    Science.gov (United States)

    González, Sergio; Pérez, Pablo; Rossinyol, Emma; Suriñach, Santiago; Dolors Baró, Maria; Pellicer, Eva; Sort, Jordi

    2014-06-01

    The microstructure and mechanical properties of Zr48Cu48 - x Al4M x (M ≡ Fe or Co, x = 0, 0.5, 1 at.%) metallic glass (MG) composites are highly dependent on the amount of Fe or Co added as microalloying elements in the parent Zr48Cu48Al4 material. Addition of Fe and Co promotes the transformation from austenite to martensite during the course of nanoindentation or compression experiments, resulting in an enhancement of plasticity. However, the presence of Fe or Co also reduces the glass forming ability, ultimately causing a worsening of the mechanical properties. Owing to the interplay between these two effects, the compressive plasticity for alloys with x = 0.5 (5.5% in Zr48Cu47.5Al4Co0.5 and 6.2% in Zr48Cu47.5Al4Fe0.5) is considerably larger than for Zr48Cu48Al4 or the alloys with x = 1. Slight variations in the Young's modulus (around 5-10%) and significant changes in the yield stress (up to 25%) are also observed depending on the composition. The different microstructural factors that have an influence on the mechanical behavior of these composites are investigated in detail: (i) co-existence of amorphous and crystalline phases in the as-cast state, (ii) nature of the crystalline phases (austenite versus martensite content), and (iii) propensity for the austenite to undergo a mechanically-driven martensitic transformation during plastic deformation. Evidence for intragranular nanotwins likely generated in the course of the austenite-martensite transformation is provided by transmission electron microscopy. Our results reveal that fine-tuning of the composition of the Zr-Cu-Al-(Fe,Co) system is crucial in order to optimize the mechanical performance of these bulk MG composites, to make them suitable materials for structural applications.

  20. Drastic influence of minor Fe or Co additions on the glass forming ability, martensitic transformations and mechanical properties of shape memory Zr-Cu-Al bulk metallic glass composites

    Science.gov (United States)

    González, Sergio; Pérez, Pablo; Rossinyol, Emma; Suriñach, Santiago; Baró, Maria Dolors; Pellicer, Eva; Sort, Jordi

    2014-06-01

    The microstructure and mechanical properties of Zr48Cu48 - x Al4M x (M ≡ Fe or Co, x = 0, 0.5, 1 at.%) metallic glass (MG) composites are highly dependent on the amount of Fe or Co added as microalloying elements in the parent Zr48Cu48Al4 material. Addition of Fe and Co promotes the transformation from austenite to martensite during the course of nanoindentation or compression experiments, resulting in an enhancement of plasticity. However, the presence of Fe or Co also reduces the glass forming ability, ultimately causing a worsening of the mechanical properties. Owing to the interplay between these two effects, the compressive plasticity for alloys with x = 0.5 (5.5% in Zr48Cu47.5Al4Co0.5 and 6.2% in Zr48Cu47.5Al4Fe0.5) is considerably larger than for Zr48Cu48Al4 or the alloys with x = 1. Slight variations in the Young’s modulus (around 5-10%) and significant changes in the yield stress (up to 25%) are also observed depending on the composition. The different microstructural factors that have an influence on the mechanical behavior of these composites are investigated in detail: (i) co-existence of amorphous and crystalline phases in the as-cast state, (ii) nature of the crystalline phases (austenite versus martensite content), and (iii) propensity for the austenite to undergo a mechanically-driven martensitic transformation during plastic deformation. Evidence for intragranular nanotwins likely generated in the course of the austenite-martensite transformation is provided by transmission electron microscopy. Our results reveal that fine-tuning of the composition of the Zr-Cu-Al-(Fe,Co) system is crucial in order to optimize the mechanical performance of these bulk MG composites, to make them suitable materials for structural applications.

  1. Super-plastic forming process of Zr-based bulk metallic glass%Zr基非晶合金超塑性成形工艺研究

    Institute of Scientific and Technical Information of China (English)

    廖广兰; 王俊; 喻强; 朱志靖

    2011-01-01

    采用感应耦合等离子体刻蚀工艺制备了微型硅模具,基于硅模具研究了非晶合金Zr41.25Ti13.75Ni10Cu12.5Be22.5的超塑性微零件成形工艺.采用差示扫描量热仪测定了Zr41.25Ti13.75Ni10Cu12.5Be22.5的过冷液相区间为360~440℃,在过冷液相区间热压成形非晶合金微零件、机械研磨去除零件飞边和采用40%的KOH溶液腐蚀去除硅模具,得到非晶合金微型零件.自主研制了成形设备,仿真分析与实验相结合,解决了成形过程中设备的温度控制问题,比较分析了不同温度下的成形结果,实验与仿真结果符合较好.在410℃条件下成功制备出模数0.03、齿数66和厚度500μm的微型内齿轮,齿形轮廓清晰,X射线衍射仪扫描结果显示该微齿轮为非晶结构,从而验证了采用该工艺制备微型零件的可行性.%Super-plastic micro-forming process of bulk metallic glasses Zr41.25Ti13.75Ni10Cu12.5Be22.5 utilizing micro silicon molds was investigated,where the micro silicon molds were fabricated by inductively coupled plasma etching.The super-cooled liquid region,360~440 ℃,was measured by differential scanning calorimeter.Micro components were thermoformed in the super-cooled liquid region.The flash of micro components was removed by mechanical grinding,and the silicon molds were resolved with 40% KOH.Forming equipment was developed on the basis of the super-plastic process,and the temperature-control was solved by simulation analysis and experiments.Subsequently,the forming results in different temperatures were analyzed,which confirmed the simulation results.Finally,an internal gear with 0.03 module,66 teeth and 500 μm thickness was obtained with good dimensional accuracy at 410 ℃.The gear had a relatively good profile with an amorphous structure proved by X-ray diffraction scanning,which substantiated the feasibility of the process.

  2. Stability of bulk metallic glass structure

    Energy Technology Data Exchange (ETDEWEB)

    Jain, H.; Williams, D.B.

    2003-06-18

    The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub (80-x)}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

  3. Cavitation instability in bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    Dai L.H.

    2015-01-01

    Full Text Available Recent experiments have shown that fracture surfaces of bulk metallic glasses (BMGs usually exhibit an intriguing nanoscale corrugation like fractographic feature mediated by nanoscale void formation. We attribute the onset of this nanoscale corrugation to TTZs (tension transformation zones mediated cavitation. In our recent study, the spall experiments of Zr-based BMG using a single-stage light gas gun were performed. To uncover the mechanisms of the spallation damage nucleation and evolution, the samples were designed to be subjected to dynamic tensile loadings of identical amplitude but with different durations by making use of the multi-stress pulse and the double-flyer techniques. It is clearly revealed that the macroscopic spall fracture in BMGs originates from the nucleation, growth and coalescence of micro-voids. Then, a microvoid nucleation model of BMGs based on free volume theory is proposed, which indicates that the nucleation of microvoids at the early stage of spallation in BMGs is resulted from diffusion and coalescence of free volume. Furthermore, a theoretical model of void growth in BMGs undergoing remote dynamic hydrostatic tension is developed. The critical condition of cavitation instability is obtained. It is found that dynamic void growth in BMGs can be well controlled by a dimensionless inertial number characterizing the competition between intrinsic and extrinsic time scales. To unveil the atomic-level mechanism of cavitation, a systematic molecular dynamics (MD simulation of spallation behaviour of a binary metallic glass with different impact velocities was performed. It is found that micro-void nucleation is determined TTZs while the growth is controlled by shear transformation zones (STZs at atomic scale.

  4. Minor alloying behavior in bulk metallic glasses and high-entropy alloys

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effect of minor alloying on several bulk metallic glasses and high-entropy al-loys was studied. It was found that minor Nb addition can optimize the interface structure between the W fiber and the Zr-based bulk metallic glass in the compos-ites,and improve the mechanical properties. Minor Y addition can destabilize the crystalline phases by inducing lattice distortion as a result to improve the glass-forming ability,and the lattice distortion energy is closely related to the effi-ciency of space filling of the competing crystalline phases. A long-period ordered structure can precipitate in the Mg-based bulk metallic glass by yttrium alloying. For the high-entropy alloys,solid solution can be formed by alloying,and its me-chanical properties can be comparable to most of the bulk metallic glasses.

  5. Do atmospheric aerosols form glasses?

    OpenAIRE

    Zobrist, B.; Marcolli, C.; Pedernera, D. A.; Koop, T.

    2008-01-01

    A new process is presented by which water soluble organics might influence ice nucleation, ice growth, chemical reactions and water uptake of aerosols in the upper troposphere: the formation of glassy aerosol particles. Glasses are disordered amorphous (non-crystalline) solids that form when a liquid is cooled without crystallization until the viscosity increases exponentially and molecular diffusion practically ceases. The glass transition temperatures, Tg

  6. Preparation of Cu-based Bulk Metallic Glass Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    Yufeng SUN; Yuren WANG; Bingchen WEI; Weihuo LI

    2006-01-01

    Cu47Ti34Zr11Ni8 bulk metallic glass (BMG) matrix composites containing in situ formed TiC particles and δ-TiCu dendrite phase were developed by copper mold cast. The thermal stability and microstructure of the composites are investigated. Room temperature compression tests reveal that the composite samples exhibit higher fracture strength and distinct plastic strain of 0.2%~0.5%, comparing with that of the corresponding Cu47Ti34Zr11 Ni8 monolithic BMG.

  7. Fe-based bulk metallic glasses used for magnetic shielding

    Science.gov (United States)

    Şerban, Va; Codrean, C.; Uţu, D.; Ercuţa, A.

    2009-01-01

    The casting in complex shapes (tubullar) and the main magnetic properties of bulk metallic glasses (BMG) alloys from the ferromagnetic Fe-Cr-Ni-Ga-P-Si-C system, with a small adittion of Ni (3%) were studied. Samples as rods and sockets having the thickness up to 1 mm were obtained from master alloys by melt injection by low cooling rates into a Cu mold and annealed in order to ensure adequate magnetic requirements. The structure was examined by X-ray diffraction (XRD) and the basic magnetic properties (coercivity, magnetic remanence, initial susceptibility, etc.) were determined by conventional low frequency induction method. The experimental investigations on producing of BMG ferromagnetic alloys with 3% Ni show the possibility to obtain magnetic shields of complex shape with satisfactory magnetic properties. The presence of Ni does not affect the glass forming ability, but reduce the shielding capacity.

  8. Formation of ternary Mg–Cu–Dy bulk metallic glasses

    Indian Academy of Sciences (India)

    X F Wu; Y Kang; F F Wu; K Q Qiu; L K Meng

    2011-12-01

    The glass-forming ability (GFA) of ternary Mg–Cu–Dy alloys was systematically investigated by using differential scanning calorimetry (DSC) and X-ray diffractometry (XRD) techniques. The results showed that a series of ternary Mg–Cu–Dy bulk metallic glasses (BGMs) with a diameter of 4–8 mm were successfully fabricated in the system with conventional Cu-mold casting method. Mg55Cu32Dy13, Mg60Cu27Dy13, Mg65Cu25Dy10 and Mg70Cu17Dy13 BMGs exhibit a clear glass transition, a broad supercooled liquid region and different crystallization and melting behaviours. They have supercooled liquid region ($\\Delta T_{x}$) from 41 K to 65 K, reduced glass transition temperature ($T_{rg}$) from 0.5363 to 0.5974 and parameter from 0.4038 to 0.4136. The shows a relatively good agreement with the GFA of the BGMs. On the other hand, a high fracture compressive strength of 624 MPa was obtained for Mg60Cu27Dy13 BMG.

  9. Comparing the density of states of binary Lennard-Jones glasses in bulk and film

    Science.gov (United States)

    Ghosh, Jayeeta; Faller, Roland

    2008-03-01

    We used Wang-Landau density of states Monte Carlo to study a binary Lennard-Jones glass-forming mixture in bulk and films between noninteracting walls. Thermodynamic properties are calculated using two different ensembles and film data are compared with the bulk. Bulk properties are in good agreement with previous simulations. We confirm the formation of a glass using various properties, e.g., energy, heat capacity, and pressure with temperature. We find a change in slope in the energy per particle and pressure as a function of temperature. We do not find any defined crystal structure. A higher glass transition temperature is found for the film.

  10. Non-isothermal crystallization kinetics and glass-forming ability of Ti{sub 41}Zr{sub 25}Be{sub 28}Fe{sub 6} bulk metallic glass investigated by differential scanning calorimetry

    Energy Technology Data Exchange (ETDEWEB)

    Gong, Pan; Zhao, Shaofan; Yao, Kefu [Tsinghua University, School of Materials Science and Engineering, Beijing (China); Wang, Xin [Hebei University of Technology, School of Materials Science and Engineering, Tianjin (China)

    2015-07-15

    The non-isothermal crystallization kinetics and glass-forming ability of Ti{sub 41}Zr{sub 25}Be{sub 28}Fe{sub 6} glassy alloy were investigated by differential scanning calorimetry. The activation energies corresponding to the characteristic temperatures have been calculated by Kissinger and Ozawa equations. Based on Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall models, it has been found that the local activation energy is higher at the beginning of the crystallization process for the first exothermic peak. The local Avrami exponent indicates that the first-step crystallization is mainly a high-dimensional nucleation and growth with an increasing nucleation rate. According to the calculated fragility index, Ti{sub 41}Zr{sub 25}Be{sub 28}Fe{sub 6} alloy can be classified as ''strong glass former.'' The studied alloy also possesses a critical size up to centimeter order, and the high glass-forming ability is probably related to the relatively low Gibbs energy difference between the liquid and crystalline states. The critical cooling rate of Ti{sub 41}Zr{sub 25}Be{sub 28}Fe{sub 6} glassy alloy has also been determined using Barandiaran-Colmenero's method. (orig.)

  11. Advanced Manufacturing Technologies (AMT): Bulk Metallic Glass Element

    Data.gov (United States)

    National Aeronautics and Space Administration — The first major objective of the ‘Bulk Metallic Glasses (BMGs) for Space Applications’ project is to raise the technology readiness level dry lubricated,...

  12. Glass Formability and Soft Magnetic Properties of Bulk Y-Fe-B-Ti Metals

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The Ti effects on the glass forming ability and the magnetic properties of Y-Fe-B-Ti bulk metallic glasses have been investigated. Substituting 2 and 4 at% Ti for Fe or B in Y6Fe70B22 alloys decrease the saturation magnetization (σs) and deteriorate the glass forming ability, respectively. However, substitution of 2 at% Ti for Y in Y6Fe72B22 alloy induces larger supercooled region of 72.7℃, which not only makes the bulk glassy rod as large as 3mm in diameter, but also results in the superior soft magnetic properties of σ5=126emu/g,coercivity ( Hc ) = 0.2 Oe and Curie temperature (Tc) = 268℃. Among all Y-Fe-B-Ti bulk amorphous rods, Y4Fe72B22Ti2 displays the best glass forming ability and also the proper soft magnetic properties.

  13. Roles of Co element in Fe-based bulk metallic glasses utilizing industrial FeB alloy as raw material

    Directory of Open Access Journals (Sweden)

    Shouyuan Wang

    2017-08-01

    Full Text Available A series of Fe-based bulk metallic glasses were fabricated by a conventional copper mold casting method using a kind of Fe-B industrial raw alloy. It is found that Fe-B-Y-Nb bulk metallic glass with 3 at% of Co addition possesses the best glass forming ability, thermal stability, hardness, magnetic property and anti-corrosion property. The hardness test result indicates a synchronically trend with glass-forming ability parameters. The excellent glass-forming ability and a combination of good mechanical and functional properties suggest that the alloys in this work might be good candidates for commercial use.

  14. Mechanical and Structural Investigation of Porous Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Baran Sarac

    2015-06-01

    Full Text Available The intrinsic properties of advanced alloy systems can be altered by changing their microstructural features. Here, we present a highly efficient method to produce and characterize structures with systematically-designed pores embedded inside. The fabrication stage involves a combination of photolithography and deep reactive ion etching of a Si template replicated using the concept of thermoplastic forming. Pt- and Zr-based bulk metallic glasses (BMGs were evaluated through uniaxial tensile test, followed by scanning electron microscope (SEM fractographic and shear band analysis. Compositional investigation of the fracture surface performed via energy dispersive X-ray spectroscopy (EDX, as well as Auger spectroscopy (AES shows a moderate amount of interdiffusion (5 at.% maximum of the constituent elements between the deformed and undeformed regions. Furthermore, length-scale effects on the mechanical behavior of porous BMGs were explored through molecular dynamics (MD simulations, where shear band formation is observed for a material width of 18 nm.

  15. Recent progress in criterions for glass forming ability

    Institute of Scientific and Technical Information of China (English)

    YANG Bing; DU Yong; LIU Yong

    2009-01-01

    The glass-forming ability(GFA) is an important factor in studying metallic glasses. So far, there are several criteria for evaluating the glass-forming ability. For predicting compositions for bulk metallic glasses, however, they show more or less accuracy and versatility for different cases. In this work, four types of criteria for the glass-forming ability are categorized and reviewed: 1) Indicators with characteristic temperatures; 2) Indicators involving structural factors; 3) Indicators based on Miedema's model; and 4) Indictors based on phase diagram. It is pointed out that a single indicator cannot be used to predict GFA of all the metallic glass systems correctly due to its limited theoretical framework, and the combination of multiple indicators shows more efficiency and accuracy. Though it is still very difficult to develop a universal indicator for GFA, recent indicators seem to be of more reliable physical meaning than those previously suggested.

  16. Failure by fracture in bulk metal forming

    DEFF Research Database (Denmark)

    Silva, C.M.A.; Alves, Luis M.; Nielsen, Chris Valentin

    2015-01-01

    This paper revisits formability in bulk metal forming in the light of fundamental concepts of plasticity,ductile damage and crack opening modes. It proposes a new test to appraise the accuracy, reliability and validity of fracture loci associated with crack opening by tension and out-of-plane she...

  17. Do atmospheric aerosols form glasses?

    Science.gov (United States)

    Zobrist, B.; Marcolli, C.; Pedernera, D. A.; Koop, T.

    2008-09-01

    A new process is presented by which water soluble organics might influence ice nucleation, ice growth, chemical reactions and water uptake of aerosols in the upper troposphere: the formation of glassy aerosol particles. Glasses are disordered amorphous (non-crystalline) solids that form when a liquid is cooled without crystallization until the viscosity increases exponentially and molecular diffusion practically ceases. The glass transition temperatures, Tg, homogeneous ice nucleation temperatures, Thom, and ice melting temperatures, Tm, of various aqueous inorganic, organic and multi-component solutions are investigated with a differential scanning calorimeter. The investigated solutes are: various polyols, glucose, raffinose, levoglucosan, an aromatic compound, sulfuric acid, ammonium bisulfate and mixtures of dicarboxylic acids (M5), of dicarboxylic acids and ammonium sulfate (M5AS), of two polyols, of glucose and ammonium nitrate, and of raffinose and M5AS. The results indicate that aqueous solutions of the investigated inorganic solutes show Tg values that are too low to be of atmospheric importance. In contrast, aqueous organic and multi-component solutions readily form glasses at low but atmospherically relevant temperatures (≤230 K). To apply the laboratory data to the atmospheric situation, the measured phase transition temperatures were transformed from a concentration to a water activity scale by extrapolating water activities determined between 252 K and 313 K to lower temperatures. The obtained state diagrams reveal that the higher the molar mass of the aqueous organic or multi-component solutes, the higher Tg of their respective solutions at a given water activity. To a lesser extent, Tg also depends on the hydrophilicity of the organic solutes. Therefore, aerosol particles containing larger (≳150 g mol-1) and more hydrophobic organic molecules are more likely to form glasses at intermediate to high relative humidities in the upper troposphere

  18. Do atmospheric aerosols form glasses?

    Directory of Open Access Journals (Sweden)

    D. A. Pedernera

    2008-09-01

    Full Text Available A new process is presented by which water soluble organics might influence ice nucleation, ice growth, chemical reactions and water uptake of aerosols in the upper troposphere: the formation of glassy aerosol particles. Glasses are disordered amorphous (non-crystalline solids that form when a liquid is cooled without crystallization until the viscosity increases exponentially and molecular diffusion practically ceases. The glass transition temperatures, Tg, homogeneous ice nucleation temperatures, Thom, and ice melting temperatures, Tm, of various aqueous inorganic, organic and multi-component solutions are investigated with a differential scanning calorimeter. The investigated solutes are: various polyols, glucose, raffinose, levoglucosan, an aromatic compound, sulfuric acid, ammonium bisulfate and mixtures of dicarboxylic acids (M5, of dicarboxylic acids and ammonium sulfate (M5AS, of two polyols, of glucose and ammonium nitrate, and of raffinose and M5AS. The results indicate that aqueous solutions of the investigated inorganic solutes show Tg values that are too low to be of atmospheric importance. In contrast, aqueous organic and multi-component solutions readily form glasses at low but atmospherically relevant temperatures (≤230 K. To apply the laboratory data to the atmospheric situation, the measured phase transition temperatures were transformed from a concentration to a water activity scale by extrapolating water activities determined between 252 K and 313 K to lower temperatures. The obtained state diagrams reveal that the higher the molar mass of the aqueous organic or multi-component solutes, the higher Tg of their respective solutions at a given water activity. To a lesser extent, Tg also depends on the hydrophilicity of the organic solutes. Therefore, aerosol particles containing larger (≳150 g mol−1 and

  19. Do atmospheric aerosols form glasses?

    Directory of Open Access Journals (Sweden)

    B. Zobrist

    2008-05-01

    Full Text Available A new process is presented by which water-soluble organics might influence ice nucleation, ice growth, chemical reactions and water uptake of aerosols in the upper troposphere: the formation of glassy aerosol particles. Glasses are disordered amorphous (non-crystalline solids that form when a liquid is cooled without crystallization until the viscosity increases exponentially and molecular diffusion practically ceases. The glass transition temperatures, Tg, homogeneous ice nucleation temperatures, Thom, and ice melting temperatures, Tm, of various aqueous inorganic, organic and multi-component solutions are investigated with a differential scanning calorimeter. The investigated solutes are: various polyols, glucose, raffinose, levoglucosan, an aromatic compound, sulfuric acid, ammonium bisulphate and mixtures of dicarboxylic acids (M5, of dicarboxylic acids and ammonium sulphate (M5AS, of two polyols, of glucose and ammonium nitrate, and of raffinose and M5AS. The results indicate that aqueous solutions of the investigated inorganic solutes show Tg-values that are too low to be of atmospheric importance. In contrast, aqueous organic and multi-component solutions readily form glasses at low but atmospherically relevant temperatures (≤230 K. To apply the laboratory data to the atmospheric situation, the measured phase transition temperatures were transformed from a concentration to a water activity scale by extrapolating water activities determined between 252 K and 313 K to lower temperatures. The obtained state diagrams reveal that the higher the molar mass of the aqueous organic or multi-component solutes, the higher Tg of their respective solutions at a given water activity. To a lesser extent, Tg also depends on the hydrophilicity of the organic solutes. Therefore, aerosol particles containing larger and more hydrophobic organic

  20. Crystallization Kinetics of Misch Metal Based Bulk Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The crystallization kinetics of Mm55Al25Cu10Ni5Co5 bulk metallic glass (BMG) was investigated by means of differential scanning calorimetry (DSC) in the mode of continuous heating or isothermal annealing. It was found that the apparent activation energy Eg, Ex and Ep of the BMG calculated by Kissinger's method were 189.58, 170.68 and 170.41 kJ·mol-1, respectively, which was bigger than those of La55Al25Cu10Ni5Co5 BMG indicating that thermal stability of the former was higher than that of the latter. The local activation energy obtained using Ozawa equation decreased as crystallization proceeded except for the initial stage. The Avrami exponents were calculated to be in the range of 3.26~5.23 for different crystallization stages and isothermal temperatures. This implied that crystallization of Mm55Al25Cu10Ni5Co5 BMG was governed by diffusion-controlled three-dimensional growth with either reduced or increased nucleation rate, depending on isothermal temperature. Inconsistency of thermal stability with glass-forming ability for Mm(La)-Al-Cu-Ni-Co BMGs was discussed.

  1. Fe-B-Y-Nb bulk metallic glasses in relation to clusters

    Institute of Scientific and Technical Information of China (English)

    CHENG Xu; WANG Qing; CHEN WeiRong; DONG Chuang

    2008-01-01

    Bulk metallic glass formations in the Fe-B-Y-Nb quaternary alloy system were in-vestigated by using the cluster line rule in combination with the minor alloying principle. The Fe-B-Y ternary system was selected as the basic system and the intersections of cluster lines were taken as the basic ternary compositions. The basic compositions were further alloyed with minor amounts of Nb. After 3-5 at.% Nb was added, the basic composition Fe68.6B25.7Y5.7, which was developed from the most densely packed cluster Fe8B3, formed 3 mm bulk metallic glasses. These quaternary bulk metallic glasses (Fe68.6B25.7Y5.7)100-xNbx (x=3-5at. %) are expressed approximately with a unified simple composition formula: (Fe8B3)1(Y, Nb)1. The (Fe68.6B25.7Y5.7)97Nb3 bulk metallic glass has the largest glass forming ability with the following characteristic parameters Tg=907 K, Tx=1006 K, Tg/T1=0.644, γ= 0.434, and Iongness t=22 mm. The combination of the cluster line rule and the minor-alloying principle is a promising new route towards the quantitative composition design of multi-component metallic glasses.

  2. Fe-B-Y-Nb bulk metallic glasses in relation to clusters

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Bulk metallic glass formations in the Fe-B-Y-Nb quaternary alloy system were in-vestigated by using the cluster line rule in combination with the minor alloying principle. The Fe-B-Y ternary system was selected as the basic system and the intersections of cluster lines were taken as the basic ternary compositions. The basic compositions were further alloyed with minor amounts of Nb. After 3-5 at.% Nb was added,the basic composition Fe68.6B25.7Y5.7,which was developed from the most densely packed cluster Fe8B3,formed 3 mm bulk metallic glasses. These quaternary bulk metallic glasses (Fe68.6B25.7Y5.7)100-xNbx (x=3-5 at.%) are expressed approximately with a unified simple composition formula: (Fe8B3)1(Y,Nb)1. The (Fe68.6B25.7Y5.7)97Nb3 bulk metallic glass has the largest glass forming ability with the following characteristic parameters Tg=907 K,Tx=1006 K,Tg/Tl=0.644,γ=0.434,and longness t=22 mm. The combination of the cluster line rule and the minor-alloying principle is a promising new route towards the quantitative composition design of multi-component metallic glasses.

  3. Spectral descriptors for bulk metallic glasses based on the thermodynamics of competing crystalline phases

    CERN Document Server

    Perim, Eric; Liu, Yanhui; Toher, Cormac; Gong, Pan; Li, Yanglin; Simmons, W Neal; Levy, Ohad; Vlassak, Joost J; Schroers, Jan; Curtarolo, Stefano

    2016-01-01

    Metallic glasses have attracted considerable interest in recent years due to their unique combination of superb properties and processability. Predicting bulk metallic glass formers from known parameters remains a challenge and the search for new systems is still performed by trial and error. It has been speculated that some sort of "confusion" during crystallization of the crystalline phases competing with glass formation could play a key role. Here, we propose a heuristic descriptor quantifying confusion and demonstrate its validity by detailed experiments on two well-known glass forming alloy systems. With the insight provided by these results, we develop a robust model for predicting glass formation ability based on the spectral decomposition of geometrical and energetic features of crystalline phases calculated ab-initio in the AFLOW high throughput framework. Our findings indicate that the formation of metallic glass phases could be a much more common phenomenon than currently estimated, with more than ...

  4. Simulation of Glass Fiber Forming Processes

    DEFF Research Database (Denmark)

    Von der Ohe, Renate

    Two glass fiber forming processes have been simulated using FEM, which are the drawing of continuous glass fibers for reinforcement purposes and the spinning of discontinuous glass fibers - stone wool for insulation. The aim of this work was to set up a numerical model for each process, and to use...

  5. Effects of density difference of constituent elements on glass formation in TiCu-based bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    Zhongyan Zhang; Zengbao Jiao; Jie Zhou; Yuan Wu; Hui Wang; Xiongjun Liu; Zhaoping Lun

    2013-01-01

    Glass formation is generally favored by a large atomic size mismatch among constituent elements, which usually leads to large density differences among them as well. During melting, elemental segregation occurs due to Stokes’ law and then inevitably affects glass formation. In this paper, such effects on glass-forming ability in a TiCu-based alloy system have been demonstrated. In the bulk glass-forming composition Ti43Cu42Hf14Si1, macroscopic segregation of Si was observed in the as-melted ingots and silicon was completely depleted in the as-cast rods. In another Ti33Cu47Ni8Zr11Si1 alloy, nevertheless, the effects of density differences among the constituent elements were less severe. It was also confirmed that using proper pre-alloys could be an effective way in alleviating the side effects of the elemental segregation.

  6. Recent results on bulk laser damage threshold of optical glasses

    Science.gov (United States)

    Jedamzik, Ralf; Elsmann, Frank

    2013-02-01

    Modern pulsed laser applications cover a broad range of wavelength, power and pulse widths. Beam guiding optics in laser systems do not only have specific requirements on the imaging quality but also have to withstand high laser power. The laser damage threshold of an optical component depends on the surface (polishing, coating ...) and also on the bulk material properties. Actual values of bulk laser damage thresholds, particularly at pulse lengths less than 1 nanosecond (1 ns), of optical glasses are rarely found in literature, except for fused silica, which is known as a key optical material for components in high power laser. However, fused silica is rather expensive and limited in optical properties. That is the reason why customers often ask for laser damage threshold data of optical glasses. Therefore, SCHOTT has started a project for the characterization of the bulk laser damage threshold of optical glasses at the wavelengths 532 nm and 1064 nm with pulse lengths in the nano- and pico-second range. Bulk and surface laser damage testing has been performed by the Laser Zentrum Hannover in Germany according to the S-on-1 test of DIN EN ISO 11254-2 / DIN EN ISO 21254.

  7. Absorbability of bulk sol-gel bioactive glasses

    Energy Technology Data Exchange (ETDEWEB)

    Hamadouche, M.; Meunier, A.; Blanchat, C.; Sedel, L. [Paris-7 Univ. (France). Lab. de Recherches Orthopediques; Greenspan, D.C.; Zhong, J.P.; Torre, G.P. la [US Biomaterials Corp., Alachua, FL (United States)

    2001-07-01

    Melt-derived bioactive glasses have been used with success in various clinical applications for over 10 years. Recently, particles of sol-gel derived bioactive glasses with an initial high specific area have exhibited high osteoconductive properties, but also a significant degradability. In this work, we explored the in-vivo bioactivity and degradability of bulk sol-gel derived glasses. Two sol-gel compositions (58S and 77S Bioglass) were used. Bulk 45S5 were used as a control. Both sol-gel derived demonstrated similar osteoconductive properties to 45S% Bioglass. In addition, absorbability was observed for sol-gel derived glasses after 12 weeks of implantation. Total absorption reached 40% after 52 weeks. No degradation could be measured in the case of 45S5 melt derived Bioglass. The degradation process was highly time dependent as demonstrated by regression analysis. New bone formation was found to fill in areas that had been resorbed similar to bone remodeling. New bone was found to fill in areas that had been absorbed, similar to natural bone remodeling. This absorbability can be assumed to be at least partially related to an osteoclastic resorption, as viable osteoclasts-like cells were found directly in contact with the glass surfaces. (orig.)

  8. Structural features of plastic deformation in bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Scudino, S., E-mail: s.scudino@ifw-dresden.de; Shakur Shahabi, H.; Stoica, M.; Kühn, U. [IFW Dresden, Institut für Komplexe Materialien, D-01069 Dresden (Germany); Kaban, I.; Escher, B.; Eckert, J. [IFW Dresden, Institut für Komplexe Materialien, D-01069 Dresden (Germany); TU Dresden, Institut für Werkstoffwissenschaft, D-01062 Dresden (Germany); Vaughan, G. B. M. [European Synchrotron Radiation Facilities ESRF, BP220, 38043 Grenoble (France)

    2015-01-19

    Spatially resolved strain maps of a plastically deformed bulk metallic glass (BMG) have been created by using high-energy X-ray diffraction. The results reveal that plastic deformation creates a spatially heterogeneous atomic arrangement, consisting of strong compressive and tensile strain fields. In addition, significant shear strain is introduced in the samples. The analysis of the eigenvalues and eigenvectors of the strain tensor indicates that considerable structural anisotropy occurs in both the magnitude and direction of the strain. These features are in contrast to the behavior observed in elastically deformed BMGs and represent a distinctive structural sign of plastic deformation in metallic glasses.

  9. Developing and Characterizing Bulk Metallic Glasses for Extreme Applications

    Science.gov (United States)

    Roberts, Scott Nolan

    Metallic glasses have typically been treated as a "one size fits all" type of material. Every alloy is considered to have high strength, high hardness, large elastic limits, corrosion resistance, etc. However, similar to traditional crystalline materials, properties are strongly dependent upon the constituent elements, how it was processed, and the conditions under which it will be used. An important distinction which can be made is between metallic glasses and their composites. Charpy impact toughness measurements are performed to determine the effect processing and microstructure have on bulk metallic glass matrix composites (BMGMCs). Samples are suction cast, machined from commercial plates, and semi-solidly forged (SSF). The SSF specimens have been found to have the highest impact toughness due to the coarsening of the dendrites, which occurs during the semi-solid processing stages. Ductile to brittle transition (DTBT) temperatures are measured for a BMGMC. While at room temperature the BMGMC is highly toughened compared to a fully glassy alloy, it undergoes a DTBT by 250 K. At this point, its impact toughness mirrors that of the constituent glassy matrix. In the following chapter, BMGMCs are shown to have the capability of being capacitively welded to form single, monolithic structures. Shear measurements are performed across welded samples, and, at sufficient weld energies, are found to retain the strength of the parent alloy. Cross-sections are inspected via SEM and no visible crystallization of the matrix occurs. Next, metallic glasses and BMGMCs are formed into sheets and eggbox structures are tested in hypervelocity impacts. Metallic glasses are ideal candidates for protection against micrometeorite orbital debris due to their high hardness and relatively low density. A flat single layer, flat BMG is compared to a BMGMC eggbox and the latter creates a more diffuse projectile cloud after penetration. A three tiered eggbox structure is also tested by firing

  10. Fabrication of bulk metallic glasses by centrifugal casting method

    OpenAIRE

    R. Nowosielski; R. Babilas

    2007-01-01

    Purpose: The aim of the present work is characterization of the centrifugal casting method, apparatus andproduced amorphous materials, which are also known as bulk metallic glassesDesign/methodology/approach: The studied centrifugal casting system consists of two main parts: castingapparatus and injection system of molten alloy. The described centrifugal casting method was presented bypreparing a casting apparatus “CentriCast – 5”. The apparatus includes a cylindrical copper mold, which isrot...

  11. Introduction to bulk metallic glass composite and its recent applications

    OpenAIRE

    2011-01-01

    Bulk metallic glass (BMG) materials are hot topics in recent years, not to mention BMG matrix composites, which further improve the magnetic and mechanical properties of BMG materials. BMG and BMG matrix materials are fast developing and promising materials in modern industry due to their extraordinary properties such as high strength, low density, excellent resistibility to high temperature and corrosion. In this paper, I reviewed processing and application of several recently developed BMG ...

  12. Failure Prediction in Bulk Metal Forming Process

    Directory of Open Access Journals (Sweden)

    Ameen Topa

    2014-01-01

    Full Text Available An important concern in metal forming is whether the desired deformation can be accomplished without defects in the final product. Various ductile fracture criteria have been developed and experimentally verified for a limited number of cases of metal forming processes. These criteria are highly dependent on the geometry of the workpiece and cannot be utilized for complicated shapes without experimental verification. However, experimental work is a resource hungry process. This paper proposes the ability of finite element analysis (FEA software such as LS-DYNA to pinpoint the crack-like flaws in bulk metal forming products. Two different approaches named as arbitrary Lagrangian-Eulerian (ALE and smooth particle hydrodynamics (SPH formulations were adopted. The results of the simulations agree well with the experimental work and a comparison between the two formulations has been carried out. Both approximation methods successfully predicted the flow of workpiece material (plastic deformation. However ALE method was able to pinpoint the location of the flaws.

  13. High-rate squeezing process of bulk metallic glasses

    Science.gov (United States)

    Fan, Jitang

    2017-03-01

    High-rate squeezing process of bulk metallic glasses from a cylinder into an intact sheet achieved by impact loading is investigated. Such a large deformation is caused by plastic flow, accompanied with geometrical confinement, shear banding/slipping, thermo softening, melting and joining. Temperature rise during the high-rate squeezing process makes a main effect. The inherent mechanisms are illustrated. Like high-pressure torsion (HPT), equal channel angular pressing (ECAP) and surface mechanical attrition treatments (SMAT) for refining grain of metals, High-Rate Squeezing (HRS), as a multiple-functions technique, not only creates a new road of processing metallic glasses and other metallic alloys for developing advanced materials, but also directs a novel technology of processing, grain refining, coating, welding and so on for treating materials.

  14. Elastic Moduli Inheritance and Weakest Link in Bulk Metallic Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Stoica, Alexandru Dan [ORNL; Wang, Xun-Li [ORNL; Lu, Z.P. [University of Science and Technology, Beijing; Clausen, Bjorn [Los Alamos National Laboratory (LANL); Brown, Donald [Los Alamos National Laboratory (LANL)

    2012-01-01

    We show that a variety of bulk metallic glasses (BMGs) inherit their Young s modulus and shear modulus from the solvent components. This is attributed to preferential straining of locally solvent-rich configurations among tightly bonded atomic clusters, which constitute the weakest link in an amorphous structure. This aspect of inhomogeneous deformation, also revealed by our in-situ neutron diffraction studies of an elastically deformed BMG, suggests a scenario of rubber-like viscoelasticity owing to a hierarchy of atomic bonds in BMGs.

  15. Ductilizing Bulk Metallic Glass Composite by Tailoring Stacking Fault Energy

    Science.gov (United States)

    Wu, Y.; Zhou, D. Q.; Song, W. L.; Wang, H.; Zhang, Z. Y.; Ma, D.; Wang, X. L.; Lu, Z. P.

    2012-12-01

    Martensitic transformation was successfully introduced to bulk metallic glasses as the reinforcement micromechanism. In this Letter, it was found that the twinning property of the reinforcing crystals can be dramatically improved by reducing the stacking fault energy through microalloying, which effectively alters the electron charge density redistribution on the slipping plane. The enhanced twinning propensity promotes the martensitic transformation of the reinforcing austenite and, consequently, improves plastic stability and the macroscopic tensile ductility. In addition, a general rule to identify effective microalloying elements based on their electronegativity and atomic size was proposed.

  16. Forming Glasses from Se and Te

    Directory of Open Access Journals (Sweden)

    Pierre Lucas

    2009-10-01

    Full Text Available Despite being close neighbors on the Periodic Table, selenium and tellurium present a totally different abilities to form glasses. Se is a very good glass former, and gives rise to numerous glass compositions which are popular for their transparency in the infrared range and their stability against crystallization. These glasses can be shaped into sophisticated optical devices such as optical fibers, planar guides or lenses. Nevertheless, their transparencies are limited at about 12 μm (depending on the thickness of the optical systems due to the relatively small mass of the Se element. On the other hand, tellurium is heavier and its use in substitution for Se permits to shift the IR cutoff beyond 20 μm. However, the semimetallic nature of Te limits its glass formation ability and this glass family is known to be unstable and consequently has found application as phase change material in the Digital Versatile Disk (DVD technology. In this paper, after a review of selenide glasses and their applications, it will be shown how, in a recent past, it has been possible to stabilize tellurium glasses by introducing new elements like Ga or I in their compositions.

  17. Glass Forming Ability of Metallic Glasses Evaluated by a New Criterion

    Institute of Scientific and Technical Information of China (English)

    CAO Qing-Ping; LI Jin-Fu; ZHOU Yao-He

    2008-01-01

    The glass-forming ability (GFA) of Cu-Zr binary alloys is evaluated using the existing criteria based on calorimetric parameters, and poor relations are found. Therefore, another parameter Trk defined as Tk/Tl, in which Tk is the Kauzmann temperature and Tl the equilibrium liquidus temperature, is proposed. It exhibits good agreements with the experimental data of the Cu-Zr system and other representative bulk metallic glass formers so long as classifying them into strong or fragile category. It is suggested that kinetic effects are irrelevantly incorporated in the GFA analysis in the previous work.

  18. Stability of Bulk Metallic Glass Structure. Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Jain, H.; Williams, D. B.

    2003-06-01

    The fundamental origins of the stability of the (Pd-Ni){sub 80}P{sub 20} bulk metallic glasses (BMGs), a prototype for a whole class of BMG formers, were explored. While much of the properties of their BMGs have been characterized, their glass-stability have not been explained in terms of the atomic and electronic structure. The local structure around all three constituent atoms was obtained, in a complementary way, using extended X-ray absorption fine structure (EXAFS), to probe the nearest neighbor environment of the metals, and extended energy loss fine structure (EXELFS), to investigate the environment around P. The occupied electronic structure was investigated using X-ray photoelectron spectroscopy (XPS). The (Pd-Ni){sub 80}P{sub 20} BMGs receive their stability from cumulative, and interrelated, effects of both atomic and electronic origin. The stability of the (Pd-Ni){sub 80}P{sub 20} BMGs can be explained in terms of the stability of Pd{sub 60}Ni{sub 20}P{sub 20} and Pd{sub 30}Ni{sub 50}P{sub 20}, glasses at the end of BMG formation. The atomic structure in these alloys is very similar to those of the binary phosphide crystals near x=0 and x=80, which are trigonal prisms of Pd or Ni atoms surrounding P atoms. Such structures are known to exist in dense, randomly-packed systems. The structure of the best glass former in this series, Pd{sub 40}Ni{sub 40}P{sub 20} is further described by a weighted average of those of Pd{sub 30}Ni{sub 50}P{sub 20} and Pd{sub 60}Ni{sub 20}P{sub 20}. Bonding states present only in the ternary alloys were found and point to a further stabilization of the system through a negative heat of mixing between Pd and Ni atoms. The Nagel and Tauc criterion, correlating a decrease in the density of states at the Fermi level with an increase in the glass stability, was consistent with greater stability of the Pd{sub x}Ni{sub 80-x}P{sub 20} glasses with respect to the binary alloys of P. A valence electron concentration of 1.8 e/a, which

  19. Glass Formation, Chemical Properties and Surface Analysis of Cu-Based Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Akihisa Inoue

    2011-04-01

    Full Text Available This paper reviews the influence of alloying elements Mo, Nb, Ta and Ni on glass formation and corrosion resistance of Cu-based bulk metallic glasses (BMGs. In order to obtain basic knowledge for application to the industry, corrosion resistance of the Cu–Hf–Ti–(Mo, Nb, Ta, Ni and Cu–Zr–Ag–Al–(Nb bulk glassy alloy systems in various solutions are reported in this work. Moreover, X-ray photoelectron spectroscopy (XPS analysis is performed to clarify the surface-related chemical characteristics of the alloy before and after immersion in the solutions; this has lead to a better understanding of the correlation between the surface composition and the corrosion resistance.

  20. Phosphate-based glass fiber vs. bulk glass: Change in fiber optical response to probe in vitro glass reactivity.

    Science.gov (United States)

    Massera, J; Ahmed, I; Petit, L; Aallos, V; Hupa, L

    2014-04-01

    This paper investigates the effect of fiber drawing on the thermal and structural properties as well as on the glass reactivity of a phosphate glass in tris(hydroxymethyl)aminomethane-buffered (TRIS) solution and simulated body fluid (SBF). The changes induced in the thermal properties suggest that the fiber drawing process leads to a weakening and probable re-orientation of the POP bonds. Whereas the fiber drawing did not significantly impact the release of P and Ca, an increase in the release of Na into the solution was noticed. This was probably due to small structural reorientations occurring during the fiber drawing process and to a slight diffusion of Na to the fiber surface. Both the powders from the bulk and the glass fibers formed a Ca-P surface layer when immersed in SBF and TRIS. The layer thickness was higher in the calcium and phosphate supersaturated SBF than in TRIS. This paper for the first time presents the in vitro reactivity and optical response of a phosphate-based bioactive glass (PBG) fiber when immersed in SBF. The light intensity remained constant for the first 48h after which a decrease with three distinct slopes was observed: the first decrease between 48 and 200h of immersion could be correlated to the formation of the Ca-P layer at the fiber surface. After this a faster decrease in light transmission was observed from 200 to ~425h in SBF. SEM analysis suggested that after 200h, the surface of the fiber was fully covered by a thin Ca-P layer which is likely to scatter light. For immersion times longer than ~425h, the thickness of the Ca-P layer increased and thus acted as a barrier to the dissolution process limiting further reduction in light transmission. The tracking of light transmission through the PBG fiber allowed monitoring of the fiber dissolution in vitro. These results are essential in developing new bioactive fiber sensors that can be used to monitor bioresponse in situ.

  1. Structural behavior of Pd40Cu30Ni10P20 bulk metallic glass below and above the glass transition

    DEFF Research Database (Denmark)

    Mattern, N.; Hermann, H.; Roth, S.;

    2003-01-01

    The thermal behavior of the structure of Pd40Cu30Ni10P20 bulk metallic glass has been investigated in situ through the glass transition by means of high-temperature x-ray synchrotron diffraction. The dependence of the x-ray structure factor S(q) of the Pd40Cu30Ni10P20 glass on temperature follows...

  2. Fracture characteristics of bulk metallic glass under high speed impact

    Institute of Scientific and Technical Information of China (English)

    Sun Bao-Ru; Zhan Zai-Ji; Liang Bo; Zhang Rui-Jun; Wang Wen-Kui

    2012-01-01

    High speed impact experiments of rectangular plate-shaped Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass(BMG)were performed using a two-stage light gas gun.Under spherical shock waves with impact velocities ranging from 0.503 km/s to 4.917 km/s,obvious traces of laminated spallation at the back(free)surface and melting(liquid droplets)at the impact point were observed.The angles about 0°,17°,36°,and 90° to the shocking direction were shown in the internal samples because of the interaction between the compressive shock waves and the rarefaction waves.The compressive normal stress was found to induce the consequent temperature rise in the core of the shear band.

  3. Self-organized Criticality Behavior in Bulk Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    Jun-wei QIAO; Zhong WANG

    2016-01-01

    Serrated flows are known as repeated yielding of bulk metallic glasses (BMGs)during plastic deformation under different loading conditions,which are associated with the operation of shear banding.According to the statis-tics of some parameters,the shear avalanches can display a self-organized critical state,suggesting a large ductility of BMGs.The emergence of the self-organized criticality (SOC)behavior in different BMGs is due to the tempera-ture,strain rate,and chemical compositions.The SOC behavior is accompanied with the following phenomena:the interactions occur in the shear bands;the incubation time is longer than the relaxation time;the time interval is lac-king of typical time scale;and the spatial or temporal parameters should display a power-law distribution.

  4. Corrosion behavior of bulk metallic glasses in different aqueous solutions

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The corrosion behavior of as-cast fully amorphous, structural relaxed amorphous and crystallized Fe65.5Cr4Mo4Ga4P12C5B5.5 bulk metallic glasses (BMGs) in NaCl, HCl and NaOH solutions was investigated by electrochemical polarization and immersion methods. X-ray photoelectron spectroscopy measurements was used to analyze the changes of the elements on the alloy surface before and after immersion in various solutions. The corrosion resistance of the Fe65.5Cr4Mo4Ga4P12C5B5.5 BMG was better than its structural relaxation/crystallization counterparts and common alloys (such as stainless steel, carbonized steel, and steel) in the selected aqueous solutions. The high corrosion resistance of this alloy in corrosive solutions leads to the formation of Fe-, Cr- and Mo-enriched protective thin surface films.

  5. Three-point bending fracture characteristics of bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    This paper presents the SEM micrographs for the three-point bending fracture surfaces of Zr-based, Ce-based and Mg-based bulk metallic glasses (BMGs), which show the dimple structures in the three kinds of BMGs. The shapes of the giant plastic deformation domain on the fracture surface are similar but the sizes are different. The fracture toughness KC and the dimple structure size of the Zr-based BMG are both the largest, and those of the Mg-based BMG are the smallest. The fracture toughness KC and the dimple structure size of the Ce-based BMG are between those of the Zr-based and the Mg-based BMG. Through analyzing the data of different fracture toughnesses of the BMGs, we find that the plastic zone width follows w = (KC/σY)2/(6π).

  6. Bulk metallic glass formation in the Pd-Ni-P and Pd-Cu-P alloy systems

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, R.B.; He, Y. [Los Alamos National Lab., NM (United States). Center for Materials Science

    1996-12-11

    Bulk metallic glasses were prepared in the Pd-Ni-P and Pd-Cu-P systems using a fluxing technique. The formation of bulk amorphous Pd-Cu-P alloys was reported here for the first time. For both alloy systems, bulk glass formation requires maintaining the phosphorus content near 20 at.%. In the Pd-Ni-P system, 10-mm diameter amorphous Pd{sub x}Ni{sub 80{minus}x}P{sub 20} rods can be formed for 25 {le} x {le} 60. In the Pd-Cu-P system, 7-mm diameter amorphous Pd{sub x}Cu{sub 80{minus}x}P{sub 20} rods can be produced for 40 {le} x {le} 60. From all the ternary alloys studied, Pd{sub 40}Ni{sub 40}P{sub 20} has the highest glass formability, and 25-mm diameter amorphous cylinders, 50 mm in length, can be easily fabricated. The glass stability of the Pd-Ni-P system is wider than that of the Pd-Cu-P system. For most bulk Pd-Ni-P glasses, {Delta}T > 90 K. The {Delta}T values of bulk amorphous Pd-Cu-P alloys are considerably smaller, ranging from 27 to 73 K. The elastic constants of bulk amorphous Pd-Ni-P and Pd-Cu-P alloys were determined using a resonant ultrasound spectroscopy technique. The Pd-Ni-P glasses are slightly stiffer than the Pd-Cu-P glasses. Within each alloy system, the Young`s modulus and the bulk modulus show little change with alloy composition. Of all the bulk glass forming systems so far investigated, the ternary Pd-Ni-P system has the best glass formability. This alloy was one of the first bulk glasses discovered, yet it still remains the best in terms of glass formability. Upon replacing part of Ni by Cu, the critical cooling rates are expected to be further reduced.

  7. High thermal stability and sluggish crystallization kinetics of high-entropy bulk metallic glasses

    Science.gov (United States)

    Yang, M.; Liu, X. J.; Ruan, H. H.; Wu, Y.; Wang, H.; Lu, Z. P.

    2016-06-01

    Metallic glasses are metastable and their thermal stability is critical for practical applications, particularly at elevated temperatures. The conventional bulk metallic glasses (BMGs), though exhibiting high glass-forming ability (GFA), crystallize quickly when being heated to a temperature higher than their glass transition temperature. This problem may potentially be alleviated due to the recent developments of high-entropy (or multi-principle-element) bulk metallic glasses (HE-BMGs). In this work, we demonstrate that typical HE-BMGs, i.e., ZrTiHfCuNiBe and ZrTiCuNiBe, have higher kinetic stability, as compared with the benchmark glass Vitreoy1 (Zr41.2Ti13.8Cu12.5Ni10Be22.5) with a similar chemical composition. The measured activation energy for glass transition and crystallization of the HE-BMGs is nearly twice that of Vitreloy 1. Moreover, the sluggish crystallization region ΔTpl-pf, defined as the temperature span between the last exothermic crystallization peak temperature Tpl and the first crystallization exothermic peak temperature Tpf, of all the HE-BMGs is much wider than that of Vitreloy 1. In addition, high-resolution transmission electron microscopy characterization of the crystallized products at different temperatures and the continuous heating transformation diagram which is proposed to estimate the lifetime at any temperature below the melting point further confirm high thermal stability of the HE-BMGs. Surprisingly, all the HE-BMGs show a small fragility value, which contradicts with their low GFA, suggesting that the underlying diffusion mechanism in the liquid and the solid of HE-BMGs is different.

  8. Ceramic and glass radioactive waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Readey, D.W.; Cooley, C.R. (comps.)

    1977-01-01

    This report contains 14 individual presentations and 6 group reports on the subject of glass and polycrystalline ceramic radioactive waste forms. It was the general consensus that the information available on glass as a waste form provided a good basis for planning on the use of glass as an initial waste form, that crystalline ceramic forms could also be good waste forms if much more development work were completed, and that prediction of the chemical and physical stability of the waste form far into the future would be much improved if the basic synergistic effects of low temperature, radiation and long times were better understood. Continuing development of the polycrystalline ceramic forms was recommended. It was concluded that the leach rate of radioactive species from the waste form is an important criterion for evaluating its suitability, particularly for the time period before solidified waste is permanently placed in the geologic isolation of a Federal repository. Separate abstracts were prepared for 12 of the individual papers; the remaining two were previously abstracted.

  9. Microstructural characterization of Mg-based bulk metallic glass and nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Babilas, Rafał, E-mail: rafal.babilas@polsl.pl [Institute of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego 18a St., 44-100 Gliwice (Poland); Nowosielski, Ryszard; Pawlyta, Mirosława [Institute of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego 18a St., 44-100 Gliwice (Poland); Fitch, Andy [European Synchrotron Radiation Facility, CS40220, 38043 Grenoble (France); Burian, Andrzej [A. Chelkowski Institute of Physics, University of Silesia, Uniwersytecka 4 St., 40-007 Katowice (Poland)

    2015-04-15

    New magnesium-based bulk metallic glasses Mg{sub 60}Cu{sub 30}Y{sub 10} have been prepared by pressure casting. Glassy alloys were successfully annealed to become nanocomposite containing 200 nm crystallites in an amorphous matrix. The microstructure of bulk glassy alloy and nanocomposite obtained during heat treatment was examined by X-ray diffraction and scanning and high-resolution electron microscopy. Metallic glass has been also studied to explain the structural characteristics by the reverse Monte Carlo (RMC) modeling based on the diffraction data. The HRTEM images allow to indicate some medium-range order (MRO) regions about 2–3 nm in size and formation of local atomic clusters. The RMC modeling results confirmed some kinds of short range order (SRO) structures. It was found that the structure of bulk metallic glass formed by the pressure casting is homogeneous. The composite material contained very small particles in the amorphous matrix. Homogeneous glassy alloy had better corrosion resistance than a composite containing nanocrystalline particles in a glassy matrix. - Highlights: • RMC modeling demonstrates some kinds of SRO structures in Mg-based BMGs. • HRTEM indicated MRO regions about 2–3 nm and SRO regions about 0.5 nm in size. • Mg-based glassy alloys were successfully annealed to become nanocomposite material. • Crystalline particles have spherical morphology with an average diameter of 200 nm. • Glassy alloy had higher corrosion resistance than a nanocomposite sample.

  10. Formation of centimeter Fe-based bulk metallic glasses in low vacuum environment

    Energy Technology Data Exchange (ETDEWEB)

    Pan Jie; Chen Qi; Li Ning [State Key Lab of Materials Processing and Mould Technology, Department of Materials Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China); Liu Lin [State Key Lab of Materials Processing and Mould Technology, Department of Materials Science and Technology, Huazhong University of Science and Technology, 430074 Wuhan (China)], E-mail: lliu2000@public.wh.hb.cn

    2008-09-08

    The formation of a Fe{sub 43.7}Co{sub 7.3}Cr{sub 14.7}Mo{sub 12.6}C{sub 15.5}B{sub 4.3}Y{sub 1.9} bulk metallic glass (BMG) was attempted in low vacuum environment and in air using commercial raw materials. The glass forming ability of the Fe-based alloys was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and differential thermal analyzer (DTA). It was found that cylindric rods with diameters ranging from 10 mm to 5 mm could be successfully fabricated by copper-mold casting in the pressures from 1.5 Pa to 10{sup 5} Pa (10{sup 5} Pa = 1 atm). All BMGs exhibit a distinct glass transition and wide supercooled liquid region. The preparation condition seems not significantly affected by the thermodynamic parameters of BMG, such as supercooled liquid region, glass transition temperature and melting process. The oxygen content of the alloys prepared in different vacuum conditions was measured by a LECO oxygen analyzer, which revealed that the oxygen content was less than 100 ppm for all BMGs prepared, even in air. The good glass forming ability and excellent oxidation resistance for the present Fe-based alloy are discussed.

  11. Glass forming ability of calcium aluminosilicate melts

    DEFF Research Database (Denmark)

    Moesgaard, Mette; Yue, Yuanzheng

    2011-01-01

    The glass forming ability (GFA) of two series of calcium aluminosilicate melts is studied by measuring their viscous behavior and crystallization tendency. The first series consists of five compositions on the joining line between the eutectic point of anorthite-wollastonite-tridymite and that of...

  12. Advanced and new developments in bulk metal forming

    DEFF Research Database (Denmark)

    Bay, Niels; Wanheim, Tarras; Ravn, Bjarne Gottlieb;

    2000-01-01

    Increasing demands to manufacturing industry of faster, better and cheaper production has intensified the research and development of bulk metal forming. The present paper gives examples on European industrial research on secondary bulk metal forming processes. The R&D follows three lines of appr...

  13. 铁基块体非晶合金玻璃形成能力与特征自由体积的关系%CORRELATION BETWEEN THE GLASS-FORMING ABILITY AND CHARACTERISTIC FREE VOLUMES OF THE IRON BASE BULK METALLIC GLASSES

    Institute of Scientific and Technical Information of China (English)

    胡强; 曾燮榕; 钱海霞; 谢胜辉; 盛洪超

    2012-01-01

    Many researches have demonstrated that the free volume have a great effect on the properties of bulk metallic glasses (BMGs). For different BMGs, however, quantitative measurement of free volumes and analysis of properties of BMGs using the measurement results are still difficult. In this work, the two types of characteristic free volumes, the free volume released in structural relaxation, △Vf-sr and the free volume generated in glass transition, △Vf_gt are given from the △(dV(T)/V0) curve, where the △(dV(T)/V0) is the thermal expansion difference between amorphous and crystalline samples measured by a cyclic thermal dilation test. In a series of Fe-(Er)-Cr-Mo-C-B BMGs, it is found that the BMG with the largest critical diameter (Dc) has also the largest △Vf_gt, and Dc increases sensitively with the decrease of △Vf-sr. More impressively, D2c or Dc can be fitted with high regression coefficient of 0.998 by a negative exponential function of △Vf-sr- Hence, the characteristic free volume has a sensitive and close correlation with the glass forming ability of BMGs.%运用循环热膨胀法获得了块体非晶合金与其晶态合金的体膨胀差曲线△(dV(T)/Vo),由此定义出块体非晶合金的2个特征自由体积,即结构弛豫中释放出的自由体积△Vf-sr和玻璃转变中生成的自由体积△Vf-gt.Fe-(Er)-Cr-Mo-C-B系列块体非晶合金的实验结果表明:非晶合金的玻璃形成能力与其特征自由体积关系密切,临界尺寸Dc最大的非晶合金的△Vf-gt也最大;且Dc随△Vf-sr变化趋势明显,D2c或Dc可以拟合成△Vf-sr的负指数函数,回归系数高达0.998.

  14. Reentrant spin glass ordering in an Fe-based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Qiang; Shen, Jun, E-mail: junshen@tongji.edu.cn [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China)

    2015-02-07

    We report the results of the complex susceptibility, temperature, and field dependence of DC magnetization and the nonequilibrium dynamics of a bulk metallic glass Fe{sub 40}Co{sub 8}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6}Er{sub 2}. Solid indication of the coexistence of reentrant spin glass (SG) and ferromagnetic orderings is determined from both DC magnetization and AC susceptibility under different DC fields. Dynamics scaling of AC susceptibility indicates critical slowing down to a reentrant SG state with a static transition temperature T{sub s} = ∼17.8 K and a dynamic exponent zv = ∼7.3. The SG nature is further corroborated from chaos and memory effects, magnetic hysteresis, and aging behavior. We discuss the results in terms of the competition among random magnetic anisotropy and exchange interactions and compare them with simulation predictions.

  15. Kinetics of Glass Transition and Crystallization in Carbon Nanotube Reinforced Mg-Cu-Gd Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter (DSC) was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite.Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.

  16. Reformation Capability of Short-Range Order and Their Medium-Range Connections Regulates Deformability of Bulk Metallic Glasses

    Science.gov (United States)

    Li, Congling; Wei, Yujie; Shi, Xinghua

    2015-07-01

    Metallic glasses (MGs) typically have high yield strength while low ductility, and the latter is commonly considered as the Achilles’ heel of MGs. Elucidate the mechanism for such low ductility becomes the research focus of this field. With molecular level simulations, we show the degree of short-range order (SRO) of atomic structure for brittle Fe-based glass decreases dramatically during the stretch, while mild change occurs in ductile Zr-based glass. The reformation capability for SRO and their medium-range connections is found to be the primary characteristics to differentiate the deformability between the two metallic glasses. We suspect that, in addition to the strength of networks formed by SRO structure, the reformation capability to reform SRO networks also plays the key role in regulating the ductility in metallic glasses. Our study provides important insights into the understanding about the mechanisms accounting for ductility or brittleness of bulk metallic glasses.

  17. Memory phenomenon in a lanthanum based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Ye [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Huang, Wei Min, E-mail: mwmhuang@ntu.edu.sg [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Zhao, Yong [School of Chemistry and Chemical Engineering, Jiangsu University, 301 Xuefu Road, Zhenjiang 212013 (China); Ding, Zhen [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore); Li, Yan [School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Tor, Shu Beng; Liu, Erjia [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 (Singapore)

    2016-07-05

    In this paper, we experimentally investigate two memory phenomena in a lanthanum based bulk metallic glass (BMG). While the temperature memory effect (TME) is not found by differential scanning calorimeter (DSC) test, shape recovery is observed in samples indented at both low and high temperatures. In terms of shape memory related characteristics, this BMG shares some features of shape memory alloys (SMAs) due to its metal nature, and some other features of shape memory polymers (SMPs) owing to its glassy–rubbery transition. The formation of protrusion in the polished sample after heating to super-cooled liquid region (SCLR) indicates that surface tension is not a necessarily positive contributor for shape recovery. Release of internal elastic stress is concluded as the major player. Although the amorphous nature of BMGs enables for storing appreciable amount of internal elastic stress upon deformation, without the presence of cross-linker as in typical SMPs, the shape recovery in BMGs is rather limited. - Highlights: • Experimental investigation of shape recovery in BMG. • Surface tension is not the major reason for shape recovery in BMG. • Release of internal stress is the major contributor for shape recovery. • Comparison of shape memory features of BMG with other shape memory materials.

  18. Fracture behaviors under pure shear loading in bulk metallic glasses

    Science.gov (United States)

    Chen, Cen; Gao, Meng; Wang, Chao; Wang, Wei-Hua; Wang, Tzu-Chiang

    2016-12-01

    Pure shear fracture test, as a special mechanical means, had been carried out extensively to obtain the critical information for traditional metallic crystalline materials and rocks, such as the intrinsic deformation behavior and fracture mechanism. However, for bulk metallic glasses (BMGs), the pure shear fracture behaviors have not been investigated systematically due to the lack of a suitable test method. Here, we specially introduce a unique antisymmetrical four-point bend shear test method to realize a uniform pure shear stress field and study the pure shear fracture behaviors of two kinds of BMGs, Zr-based and La-based BMGs. All kinds of fracture behaviors, the pure shear fracture strength, fracture angle and fracture surface morphology, are systematically analyzed and compared with those of the conventional compressive and tensile fracture. Our results indicate that both the Zr-based and La-based BMGs follow the same fracture mechanism under pure shear loading, which is significantly different from the situation of some previous research results. Our results might offer new enlightenment on the intrinsic deformation and fracture mechanism of BMGs and other amorphous materials.

  19. Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

    Science.gov (United States)

    Li, Jiawei; Huo, Juntao; Law, Jiayan; Chang, Chuntao; Du, Juan; Man, Qikui; Wang, Xinmin; Li, Run-Wei

    2014-08-01

    The effects of heavy rare earth (RE) additions on the Curie temperature (TC) and magnetocaloric effect of the Fe-RE-B-Nb (RE = Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune TC in a large temperature range of 120 K without significantly decreasing the magnetic entropy change (ΔSM) and refrigerant capacity (RC) of the alloys. The observed values of ΔSM and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd5Ge1.9Si2Fe0.1. The tunable TC and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.

  20. Dynamic mechanical behavior of a Zr-based bulk metallic glass during glass transition and crystallization

    Institute of Scientific and Technical Information of China (English)

    CHAO Qi; WANG Qing; DONG Yuanda

    2009-01-01

    The dynamic mechanical behaviors of the Zr41Ti14Cu12.5Ni8Be22.5Fe2 bulk metallic glass (BMG) during continuous heating at a constant rate were investigated. The glass transition and crystallization of the Zr-based BMG were thus characterized by the measurements of storage modulus E and internal friction Q-1. It was found that the variations of these dynamic mechanical quantifies with temperature were interre-lated and were well in agreement with the DSC trace obtained at the same heating rate. The origin of the first peak in the internal friction curve was closely related to the dynamic glass transition and subsequent primary crystallization. Moreover, it can be well described by a physical model, which can characterize atomic mobility and mechanical response of disordered condense materials. In comparison with the DSC trace, the relative position of the first internal friction peak of the BMG was found to be dependent on its thermal stability against crys-tallization.

  1. A Process for Making Bulk Heavy Metal Fluoride Glasses.

    Science.gov (United States)

    This invention relates to the preparation of glasses, and, in particular, relates to the preparation of heavy metal fluoride glasses with...reproducible high optical qualities. Considerable effort has been expended to develop heavy metal fluoride glasses ( HMFG ) as a viable family of infrared

  2. Surface Crystallization in Mg-Based Bulk Metallic Glass during Copper Mold Casting

    Directory of Open Access Journals (Sweden)

    Xin Wang

    2014-01-01

    Full Text Available The localized crystallization of Mg54Cu28Ag7Y11 bulk metallic glass (BMG in the injection casting process using a copper mold was investigated. It has been found that several crystalline phases were formed close to the as-cast surface but did not exist in the internal part of the BMG plate. It is abnormal that the as-cast surface is partially crystallized with higher cooling rate than that of inside. Overheating of the melt and nucleation induced by the surface of copper mold play key roles in the abnormal crystallization. It is suggested that the function of copper mold to trigger heterogeneous nucleation cannot be totally ignored, although it provides the high cooling rate for the glass formation during casting.

  3. Development of bulk metallic glasses based on the Dy-Al binary eutectic composition

    Institute of Scientific and Technical Information of China (English)

    LUO Lin; TIAN Rui; XIAO Xueshan

    2008-01-01

    A series of dysprosium-based ternary, quadruple, and quintuple bulk metallic glasses (BMGs) based on Dy-Al binary eutectic compo-sition were obtained with the partial substitution of Co, Gd, and Ni elements, for dysprosium. The results showed that the Dy31Gd25Co20Al24 alloy, which had the best glass forming ability (GFA), could be cast into an amorphous rod with a diameter of 5 mm. The GFA of alloys was evaluated on the basis of the supercooled liquid region width, γ parameter, the formation enthalpy, and the equivalent electronegativity difference of amor-phous alloys. It was found that the eutectic composition was closely correlated with the GFA of the Dy-based BMGs.

  4. Microstructure and mechanical properties of a novel Zr-based bulk metallic glass composite

    Institute of Scientific and Technical Information of China (English)

    SUN Yufeng; WANG Yuren; GUO Jian; WEI Bingchen; LI Weihuo

    2005-01-01

    Zr48.5Cu46.5Al5 bulk metallic glass (BMG) composites with diameters of 3 and 4 mm were prepared through suction casting in an arc melting furnace by modulating the alloy composition around the monothetic BMG composition of the high glass forming ability. Microstructural characterization reveals that the composites contain micron-sized CuZr phase with martensite structure, as well as nano-sized Zr2Cu crystalline particles and Cu10Zr7 plate-like phase embedded in an amorphous matrix. Room temperature compression tests showed that the composites exhibited significant strain hardening and obvious plastic strain of 7.7% for 3 mm and 6.4% for 4 mm diameter samples, respectively.

  5. Locating Malleable Bulk Metallic Glasses in Zr-Ti-Cu-Al Alloys with Calorimetric Glass Transition Temperature as an Indicator

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    We defined the plastic deformability under constrained loading conditions as malleability for bulk metallic glass (BMG) materials. Quaternary Zr-Ti-Cu-Al alloys in the Zr-rich composition range are selected to investigate the compositional dependence of malleability assessed by bending testing and glass transition temperature (Tg ). As indicated, increasing the Al or Cu concentration in the alloys leads to the rise of T g . The Zr(61)Ti2Cu(25)Al(12) (ZT1) and Zr(61.6)Ti(4.4)Cu(24)Al(10) (ZT3) alloys exhibit an optimal combination of lower T g and higher glass-forming ability. The malleable BMGs such as ZT1 manifests two characters during deformation, the stable propagation of a single shear band indicated by large shear offsets and easy proliferation of shear bands. With increasing the T g of BMG, the yield strength σy,Young's modulus and shear modulus simultaneously increase as well, while the Poisson s ratio decreases. The σy of ZT1 BMG is about 1680 MPa in compression and 1600 MPa in tension. In tensile loading, no any visible plasticity appears even when the strain rate increases up to the order of magnitude of 10(-1)s(-1). In consistent with the T g , malleability of Zr-Ti-Cu-Al BMGs manifests significant compositional dependence. The malleable BMG is associated with lower Tg , as well as lower shear modulus or higher Poisson s ratio, which can be understood on the basis of the correlation of Tg with shear energy barrier in metallic glass. Thus, the calorimetric Tg can be used as an indicator to screen malleable BMG-forming composition, with advantage of experimental accessibility.

  6. Fabrication and Machining of Bulk Metallic Glass for Airborne Gravity Gradiometry

    Science.gov (United States)

    Cole, Kevin Mark

    Bulk metallic glass is an intriguing material ideally suited for use as a flexure in an airborne gravity gradiometry. Successful fabrication of Zr56Ni20Al15Cu5Nb4 was achieved using arc melting and suction casting. The effect of oxygen and microalloying Nb into this alloy composition was investigated. It was determined that oxygen in solute form is much more detrimental than as an oxide with respect to glass forming ability. Through microalloying Nb, a high glass forming region was observed between 2 - 4 at.% Nb. Studies on crystallization kinetics revealed that upon heating these amorphous samples, a multi-step phase transformation pathway can be observed. Lastly, electrochemical micromachining (ECMM) and abrasive water jet machining (AWJM) were shown to be effective techniques which can be used to shape BMGs after casting without inducing crystallization. ECMM parameters were investigated to optimize the micron-machining process. AWJM demonstrated that fast cutting could be achieved with smooth surface finishes and good dimensional tolerance.

  7. The relationship between efficient packing and glass-forming ability in hard-sphere systems

    Science.gov (United States)

    Zhang, Kai

    2014-03-01

    When supercooled liquids are rapidly quenched at rates R exceeding a critical value Rc, they avoid crystallization and form amorphous solids, such as bulk metallic glasses (BMGs). However, engineering applications of BMGs are often limited by the high cost of the constituent elements and their small casting thickness. Thus, we seek to design particular alloys with controllable stoichiometry and maximal critical cooling rate Rc. We perform numerical simulations to compress binary hard-sphere mixtures into glasses as a function of the particle size ratio and stoichiometry. We measure the packing fraction and local structural order for each glass to determine the critical compression rate. We find that large packing fraction differences between the crystalline and amorphous states implies poor glass forming ability, whereas small packing fraction differences yield better glass-formers. In addition, we show that an abundance of icosahedral order in amorphous packings enhances the glass forming ability of the mixtures. NSF MRSEC DMR-1119826, DMR-1006537, CBET-0968013.

  8. Ni-based Ni-Fe-B-Si-Ta bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The glass-forming ability and properties of Ni-based Ni-Fe-B-Si-Ta bulk metallic glasses are explored in this work. The alloy compositions are determined by using a combination of the cluster line approach, the multi-alloying strategy and the substitutions of similar elements. Bulk metallic glasses with diameters of 3 mm take shape at compositions formulated under the clus- ter-plus-glue-atom model [M9B]B~[(Ni1-xFex)7.71(Si0.66Ta0.34)1.29B]B0.94=(Ni1-xFex)70.5B17.7Si7.8Ta4, x=0.35–0.45, where the bracketed part is the cluster and the unbracketed part is the glue atoms. These alloys exhibit good magnetic properties. The maximum Is is found in the (Ni0.55Fe0.45)70.5B17.7Si7.8Ta4 alloy which reaches 0.51 T, with its Hc as low as 8.5 A/m. Interestingly, these alloys display dual glass transitions at (Ni0.65Fe0.35)70.5B17.7Si7.8Ta4, (Ni0.60Fe0.4)70.5B17.7Si7.8Ta4 and (Ni0.55Fe0.45)70.5B17.7- Si7.8Ta4 as unveiled by Temperature-Modulated Differential Scanning Calorimetry.

  9. High plastic Zr-Cu-Fe-Al-Nb bulk metallic glasses for biomedical applications

    Science.gov (United States)

    Wang, Shu-shen; Wang, Yun-liang; Wu, Yi-dong; Wang, Tan; Hui, Xi-dong

    2015-06-01

    Four Zr-Cu-Fe-Al-based bulk metallic glasses (BMGs) with Zr contents greater than 65at% and minor additions of Nb were designed and prepared. The glass forming abilities, thermal stabilities, mechanical properties, and corrosion resistance properties of the prepared BMGs were investigated. These BMGs exhibit moderate glass forming abilities along with superior fracture and yield strengths compared to previously reported Zr-Cu-Fe-Al BMGs. Specifically, the addition of Nb into this quaternary system remarkably increases the plastic strain to 27.5%, which is related to the high Poisson's ratio and low Young's and shear moduli. The Nb-bearing BMGs also exhibit a lower corrosion current density by about one order of magnitude and a wider passive region than 316L steel in phosphate buffer solution (PBS, pH 7.4). The combination of the optimized composition with high deformation ability, low Young's modulus, and excellent corrosion resistance properties indicates that this kind of BMG is promising for biomedical applications.

  10. Composition optimization of the Al-Co-Zr bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yingmin; Zhang Xinfang; Qiang Jianbing; Wang Qing; Wang Dehe; Li Dejun; Shek Chanhung; Dong Chuang

    2004-03-15

    Composition optimization for locating the composition with the largest glass forming ability in the Al-Co-Zr system is attempted in this investigation. The criteria that we have developed are respectively related to a specific conduction electron concentration, termed the e/a-constant criterion, and to a specific cluster structure, termed the e/a-variant criterion. For this system, the two criteria are incarnated into the composition line with constant e/a=1.5 and the Co{sub 4}Zr{sub 9}-Al composition line. Bulk metallic glasses are obtained by suction casting for compositions with e/a=1.3-1.5, with their thermal stabilities and glass forming abilities being increased with increasing e/a ratios. The crossing point of the e/a=1.5 line and the Co{sub 4}Zr{sub 9}-Al line gives the composition Al{sub 23.5}Co{sub 23.5}Zr{sub 53} with the largest GFA (e.g. T{sub g}/T{sub m}=0.637), superior to the reported Al{sub 20}Co{sub 25}Zr{sub 55} alloy with T{sub g}/T{sub m}=0.621.

  11. Zr基大块非晶合金在过冷液相区超塑性成形的摩擦行为及机理研究%Study on the Friction Behavior and Mechanism of Zr-based Bulk Metallic Glass Superplastic Forming in the Supercooled Liquid Region

    Institute of Scientific and Technical Information of China (English)

    郑志镇; 成蛟; 王新云; 李建军

    2009-01-01

    The friction behavior of Zr_(55) Al_(10)Ni_5Cu_(30) bulk metallic glass in the supercooled liquid region was investigated. The influence of forming temperature and velocity on friction factor was established by double cup extrusion test. The calibration curves of friction factor were evaluated by FE simulation and Kawamura's constitutive equation was adopted. Constant parameters in the constitutive equation were acquired by fitting the data from compression test. The results indicate that the friction factor of bulk metallic glass forming in the supercooled liquid region is between 0. 2 and 0. 7. With the temperature rising, the friction factor decreases in general under a low forming velocity. However, the friction factor increases slightly and then decreases abruptly under a high forming velocity. In low temperature area of supercooled liquid region, the friction factor increases abruptly with increasing of the forming velocity. While in high temperature area of supercooled liquid region, the friction factor decreases slightly with increasing of the forming velocity. The friction mechanism of bulk metallic glass forming in supercooled liquid region was analyzed by modern tribology theory. Adhesion is the dominant factor contributing to the friction of bulk metallic glass.%采用双杯挤压方法研究了成形温度、应变速率等工艺参数对Zr_(55) Al_(10) Ni_5 Cu_(30)块体非晶合金在过冷液相区塑性成形时模具和零件之间的摩擦行为的影响.采用有限元模拟方法获得大块非晶合金双杯挤压的摩擦因数标定曲线,有限元模拟中非晶合金的变形采用Kawamura的本构模型,将高温压缩实验的数据拟合,获得本构模型中的参数,结果表明非晶合金在过冷液相区内变形的摩擦因数在0.2~0.7之间.当应变速率较低时,随着温度的升高,摩擦因数总体上降低;而当应变速率较高时,随着温度的升高,摩擦因数先略有上升,然后急剧下降.当温度较低

  12. A Modified Glass Formation Criterion for Various Glass Forming Liquids with Higher Reliability

    Institute of Scientific and Technical Information of China (English)

    X.H.Du; J.C.Huang

    2007-01-01

    A modified indicator of the glass forming ability (GFA) from the previous γ= Tx/(Tl+Tg) for various glass forming liquids is proposed based on a conceptual approach which combines more acceptable physical metallurgy views in terms of the time-temperature-transformation diagrams. It is found that the glass forming ability for glass forming liquids is closely associated mainly with two factors, i.e. (2Tx-Tg) and Tl (wherein Tx is the onset crystallization temperature, Tg the glass transition temperature, and Tl the liquidus temperature), and could be predicated by a unified parameter γm defined as (2Tx-Tg)/Tl. This approach is confirmed and validated by experimental data in various glass forming systems including oxide glasses, cryoprotectants and metallic glasses, which all shows a higher reliability when their glass forming ability is predicted by the modified parameter.

  13. The effect of high energy concentration source irradiation on structure and properties of Fe-based bulk metallic glass

    Science.gov (United States)

    Pilarczyk, Wirginia

    2016-06-01

    Metallic glasses exhibit metastable structure and maintain this relatively stable amorphous state within certain temperature range. High intensity laser beam was used for the surface irradiation of Fe-Co-B-Si-Nb bulk metallic glasses. The variable parameter was laser beam pulse energy. For the analysis of structure and properties of bulk metallic glasses and their surface after laser remelting the X-ray analysis, microscopic observation and test of mechanical properties were carried out. Examination of the nanostructure of amorphous materials obtained by high pressure copper mold casting method and the irradiated with the use of TITAN 80-300 HRTEM was carried out. Nanohardness and reduced Young's modulus of particular amorphous and amorphous-crystalline material zone of the laser beam were examined with the use of Hysitron TI950 Triboindenter nanoindenter and with the use of Berkovich's indenter. The XRD and microscopic analysis showed that the test material is amorphous in its structure before irradiation. Microstructure observation with electron transmission microscopy gave information about alloy crystallization in the irradiated process. Identification of given crystal phases allows to determine the kind of crystal phases created in the first place and also further changes of phase composition of alloy. The main value of the nanohardness of the surface prepared by laser beam has the order of magnitude similar to bulk metallic glasses formed by casting process irrespective of the laser beam energy used. Research results analysis showed that the area between parent material and fusion zone is characterized by extraordinarily interesting structure which is and will be the subject of further analysis in the scope of bulk metallic glasses amorphous structure and high energy concentration source. The main goal of this work is the results' presentation of structure and chosen properties of the selected bulk metallic glasses after casting process and after irradiation

  14. Thermal and mechanical properties of Cu-Zr-Al bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Cheung, T.L. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong); Shek, C.H. [Department of Physics and Materials Science, City University of Hong Kong, Tat Chee Avenue, Kowloon Tong (Hong Kong)]. E-mail: apchshek@cityu.edu.hk

    2007-05-31

    The effects of adding small amount of aluminum to the binary Cu{sub 50}Zr{sub 50} bulk metallic glass (BMG) on the thermal and mechanical properties were investigated. The Al addition was limited to 3 {<=} x {<=} 10 at.% in order to form fully amorphous bulk samples. Glassy rods of 3 mm diameter of these alloys were prepared by copper mold suction casting. The (Cu{sub 50}Zr{sub 50}){sub 100-x}Al {sub x} BMGs (x = 0 and 3 {<=} x {<=} 10 at.%) were characterized with differential scanning calorimetry (DSC), X-ray diffraction (XRD), Vickers microhardness test and nanoindentation, respectively. The glass transition temperatures, crystallization temperatures and super-cooled liquid regions of the specimens increased with increasing Al content. The microhardness of the specimens also increases with increasing Al content. Room temperature nanoindentation was carried out on the cross-section of the rods. The results showed that the nanohardness and creep displacement were dependent on the Al content.

  15. Advanced and new developments in bulk metal forming

    DEFF Research Database (Denmark)

    Bay, Niels; Wanheim, Tarras; Ravn, Bjarne Gottlieb

    2000-01-01

    Increasing demands to manufacturing industry of faster, better and cheaper production has intensified the research and development of bulk metal forming. The present paper gives examples on European industrial research on secondary bulk metal forming processes. The R&D follows three lines...... of approach, 1. the classical process development, 2. development of physical as well as numerical modelling techniques and 3. the thematic approach, where integrated analysis of the interactions between workpiece, tool and press are now possible with objectives like prediction of workpiece defects...

  16. Towards the first generation micro bulk forming system

    DEFF Research Database (Denmark)

    Arentoft, Mogens; Eriksen, Rasmus Solmer; Hansen, Hans Nørgaard

    2011-01-01

    The industrial demand for micro mechanical components has surged in the later years with the constant introduction of more integrated products. The micro bulk forming process holds a promising pledge of delivering high quality micro mechanical components at low cost and high production rates. Thi...... press. The system is demonstrated on an advanced micro forming case where a dental component is formed in medical grade Titanium....

  17. Thermodynamic model for glass forming ability of ternary metallic glass systems

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The thermodynamic model of multicomponent chemical short range order (MCSRO) was established in order to evaluate the glass forming ability (GFA) of ternary alloys. Comprehensive numerical calculations using MSCRO software were conducted to obtain the composition dependence of the MCSRO undercooling in Zr-Ni-Cu, Zr-Si-Cu and Pd-Si-Cu ternary systems. By the MCSRO undercooling principle, the composition range of Zr-Ni-Cu system with optimum GFA is determined to be 62.5~75Zr, 5~20Cu, 12.5~25Ni (n(Ni)/n(Cu)=1~5). The TTT curves of Zr-Ni-Cu system were also calculated based on the MCSRO model. The critical cooling rates for Zr-based alloy with deep MSCRO undercooling are estimated to be as low as 100?K/s, which is consistent with the practical cooling rate in the preparation of Zr-based bulk metallic glass (BMG). The calculation also illustrates that the easy glass forming systems such as Pd-based alloys exhibit an extraordinary deep MCSRO undercooling. It is shown that the thermodynamic model of MCSRO provides an effective method for the alloy designing of BMG.

  18. Are the dynamics of silicate glasses and glass-forming liquids embedded in their elastic properties?

    DEFF Research Database (Denmark)

    Smedskjær, Morten Mattrup; Mauro, John C.

    According to the elastic theory of the glass transition, the dynamics of glasses and glass-forming liquids are controlled by the evolution of shear modulus. In particular, the elastic shoving model expresses dynamics in terms of an activation energy required to shove aside the surrounding atoms, ...... of the silicate glass transition are governed by additional factors beyond the evolution of the shear modulus....

  19. Bulk metallic glass for low noise fluxgate Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The team of Prime Photonics, Virginia Tech, and Utron Kinetics propose to demonstrate a method for fabrication of a bulk, amorphous, cobalt-rich material that...

  20. Fe-based bulk metallic glasses with Y addition

    Energy Technology Data Exchange (ETDEWEB)

    Baser, Tanya Aycan [Dipartimento di Chimica IFM and NIS, Universita di Torino, Via P.Giuria, 9-10125 Torino (Italy); Baricco, Marcello [Dipartimento di Chimica IFM and NIS, Universita di Torino, Via P.Giuria, 9-10125 Torino (Italy)]. E-mail: marcello.baricco@unito.it

    2007-05-31

    This paper aims to study the role of residual vacuum during sample preparation and of quenching rate on glass formation in Fe{sub 50-x}Cr{sub 15}Mo{sub 14}Y {sub x}C{sub 15}B{sub 6} (x = 0, 2) alloys. The equilibrium phase mixture has been clarified for both alloys, combining X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements. The beneficial effects of minor addition of Y on the glass formation are evidenced. A high residual vacuum during sample preparation promotes glass formation. Glass transition temperature for amorphous sample containing 2 at.% Y is 881 K and the onset crystallization temperature is 904 K. The melting behavior for both as-cast alloys were measured with high temperature differential scanning calorimeter (HTDSC). Melting starts at 1384 K, ends at 1506 and 1470 K as liquidus temperatures for Fe{sub 50}Cr{sub 15}Mo{sub 14}C{sub 15}B{sub 6} and Fe{sub 48}Cr{sub 15}Mo{sub 14}Y{sub 2}C{sub 15}B{sub 6} alloys, respectively. The addition of Y leads to a melting behavior of as-cast sample close to eutectic, which enhances glass formation.

  1. Effects of cooling rates on the mechanical properties of a Ti-based bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Mechanical properties of the glassy specimens fabricated at different cooling rates with a composition of Ti40Zr25Cu12Ni3Be20 were systematically investigated. It was confirmed that faster cooling rates caused not only a larger amount of frozen-in free volume but also a higher glass transition temperature in the bulk glassy alloy. Increase in the free volume was found to favor plastic deformation and then to give rise to larger compressive plasticity, whilst the rise in the glass transition temperature seemed to be closely related to the higher yield strength. Moreover, the increase of yield strength and plasticity induced by fast cooling rates may also be associated with the residual stress generated during the fabrication process. Our results suggest that the deformation behavior of bulk metallic glasses is sensitive to various factors and influences from the other factors should be excluded as far as cooling-rate effects on bulk metallic glasses are considered.

  2. High-throughput Exploration of Glass Formation via Laser Deposition and the Study of Heterogeneous Microstructure in a Bulk Metallic Glass Alloy

    Science.gov (United States)

    Tsai, Peter T.

    Bulk metallic glasses are a relatively novel class of engineering alloys characterized by a "disordered" atomic structure devoid of long-range translational symmetry. Compared to crystalline alloys, the confluence of metallic bonding and amorphous structure imbues bulk metallic glasses with a unique set of properties that makes them particularly attractive for a wide variety of structural applications. Such properties include exceptional yield strengths, high elastic resilience, resistance to corrosion, and in particular, the unparalleled ability among metals to be thermoplastically formed across a wide range of length scales when heated above the glass transition temperature. Formation of metallic glass from a molten liquid depends on whether cooling is sufficiently rapid to bypass crystallization and vitrify into an amorphous solid; for a given alloy composition, the ease with which full vitrification can occur upon cooling from the liquid state is termed the alloy's "glass forming ability". Unfortunately, relatively few excellent glass formers have been reported in the vast, multicomponent composition space in which they reside. The apparent slowness of progress may be attributed largely to the inefficiency of the one-at-a-time experimental approach to discovery and design. In this thesis work, a high-throughput combinatorial methodology was developed to expedite the discovery process of new bulk metallic glasses. Laser deposition was used to fabricate continuously-graded composition libraries of Cu-Zr and Cu-Zr-Ti alloys. By processing the libraries with a range of laser heat input, the best glass formers in each alloy system could be efficiently and systematically deduced. Furthermore, instrumented nanoindentation performed on the libraries enabled rapid evaluation of mechanical property trends. Despite boasting high strengths, monolithic bulk metallic glasses generally suffer from an intrinsic lack of damage tolerance compared to other high performance alloys

  3. Glass transition, crystallization kinetics and pressure effect on crystallization of ZrNbCuNiBe bulk metallic glass

    DEFF Research Database (Denmark)

    Xing, P.F.; Zhuang, Yanxin; Wang, W.H.

    2002-01-01

    The glass transition behavior and crystallization kinetics of Zr48Nb8Cu14Ni12Be18 bulk metallic glass have been investigated by differential scanning calorimetry and x-ray powder diffraction (XRD). The activation energies of both glass transition and crystallization events have been obtained using...... effect on crystallization is studied by in situ high-pressure and high-temperature XRD using synchrotron radiation. Two crystallization temperatures, observed by in-situ XRD, behave differently with varying pressure. The onset crystallization temperature increases with pressure with a slope of 9.5 K...

  4. Vibrational dynamics of Zr-based bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    Aditya M.VORA

    2009-01-01

    The vibrational dynamics of some Zr-based bulkmetallic glasses were studied at room temperature in terms of phonon eigen frequencies of longitudinal and transverse modes employing three different approaches proposed by Hubbard-Beeby (HB), Takeno-Goda (TG) and Bhatia-Singh (BS). The well recognized model potential is employed successfully to explain electron-ion interaction in the metallic glass. The present findings of phonon dispersion curve are found to be in fair agreement with available theoretical as well as experimental data. The thermodynamic properties obtained by the HB and TG approaches are found to be much lower than those obtained by the BS approach.

  5. Tuning apparent friction coefficient by controlled patterning bulk metallic glasses surfaces

    Science.gov (United States)

    Li, Ning; Xu, Erjiang; Liu, Ze; Wang, Xinyun; Liu, Lin

    2016-12-01

    Micro-honeycomb structures with various pitches between adjacent cells were hot-embossed on Zr35Ti30Cu8.25Be26.75 bulk metallic glass surface. The effect of pitch geometry on the frictional behavior of metallic glass surface was systematically investigated. The results revealed that all textured metallic glass surfaces show a reduction in friction coefficient compared to smooth surface. More intriguingly, the friction coefficient first decreased and then increased gradually with increasing pitches. Such unique behavior can be understood fundamentally from the perspective of competing effects between contact area and local stress level with increasing pitches. This finding not only enhance the in-depth understanding of the mechanism of the significant role of surface topography on the frictional behavior of metallic glass surface, but also opens a new route towards other functional applications for bulk metallic glasses.

  6. Mie Potential and Equation of State of Zr48Nb8Cu14Ni12Be18 Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    张勇; 潘明祥; 汪卫华

    2001-01-01

    The linear expansion of Zr48Nb8Cu14Ni12Be18 bulk metallic glass (BMG) with excellent glass forming abilityand high thermal stability is investigated by a dilatometry method. The average expansion coefficient is αTG=1.04×10 -5 K-1 (300-656 K) for the BMG and αTC= 1.11×10 -5 K-1 (356~890 K) for the crystallized alloy.The Mie potential as well as the equation of state of the BMG and its corresponding crystallized state are determined from the thermal expansion and ultrasonic data, and the differences among them are phenomenologicallyexplained.

  7. Kinetics of glass transition and crystallization in multicomponent bulk amorphous alloys

    Institute of Scientific and Technical Information of China (English)

    庄艳歆[1; 赵德乾[2; 张勇[3; 汪卫华[4; 潘明祥[5

    2000-01-01

    Differential scanning calorimeter (DSC) is used to investigate apparent activation energy of glass transition and crystallization of Zr-based bulk amorphous alloys by Kissinger equation under non-isothermal condition. It is shown that the glass transition behavior as well as crystallization reaction depends on the heating rate and has a characteristic of kinetic effects. After being isothermally annealed near glass transition temperature, the apparent activation energy of glass transition increases and the apparent activation energy of crystallization reaction decreases. However, the kinetic effects are independent of the pre-annealing.

  8. Characteristics of Johari-Goldstein relaxations in bulk metallic glasses

    Science.gov (United States)

    Qiao, Jichao; Casalini, Riccardo; Pelletier, Jean-Marc; Kato, Hidemi; Yao, Yao; Yao'S Group Team; Chemistry Division, Naval Research Laboratory Team; Pvmh, Mateis, Insa de Lyon Team; Kato'S Lab Team

    2015-03-01

    The dynamics of Pd-based metallic glasses was studied by mechanical spectroscopy and modulated differential scanning calorimetry. The results show the change in composition has a significant effect on the α relaxation dynamics. All Pd-based metallic glasses have similar fragilities, 59 < m <67, and Kohlrausch stretched exponents, 0.59 <βKWW <0.60. The values of m and βKWW correlate well with the general relation proposed by Böhmer et al. for other glassy materials and the substitution of the Ni with Cu induced a large change in the time constant of the β relaxation, τβ. The activation energy, Uβ, of the β relaxation was generally independent of chemical composition. In all cases, 25 glass formers. From the heat capacity and mechanical loss, the number of dynamically correlated units, Ncwere obtained; significantly larger Nc values for these metallic glasses were observed compared with glassy materials.

  9. A modularized pulse forming line using glass-ceramic slabs.

    Science.gov (United States)

    Wang, Songsong; Shu, Ting; Yang, Hanwu

    2012-08-01

    In our lab, a kind of glass-ceramic slab has been chosen to study the issues of applying solid-state dielectrics to pulse forming lines (PFLs). Limited by the manufacture of the glass-ceramic bulk with large sizes, a single ceramic slab is hard to store sufficient power for the PFL. Therefore, a modularized PFL design concept is proposed in this paper. We regard a single ceramic slab as a module to form each single Blumlein PFL. We connect ceramic slabs in series to enlarge pulse width, and stack the ceramic Blumlein PFLs in parallel to increase the output voltage amplitude. Testing results of a single Blumlein PFL indicate that one ceramic slab contributes about 11 ns to the total pulse width which has a linear relation to the number of the ceramic slabs. We have developed a prototype facility of the 2-stage stacked Blumlein PFL with a length of 2 ceramic slabs. The PFL is dc charged up to 5 kV, and the output voltage pulse of 10 kV, 22 ns is measured across an 8 Ω load. Simulation and experiment results in good agreement demonstrate that the modularized design is reasonable.

  10. Serrated plastic flow during nanoindentation of a bulk metallic glass

    NARCIS (Netherlands)

    Golovin, YI; Ivolgin, [No Value; Khonik, VA; Kitagawa, K; Tyurin, AI

    2001-01-01

    The results of nanoindentation tests of bulk glassy Pd40CU30Ni10P20 using a specially designed instrument with high time and spatial resolution are presented. Pronounced serrations of the indenter penetration depth are observed. The parameters of serrated flow (the number of serrations, their amplit

  11. Possible causes of the change of dynamics in glass-forming materials subjected to reduced dimension

    Energy Technology Data Exchange (ETDEWEB)

    Ngai, K.L. [Naval Research Lab., Washington, DC (United States); Rizos, A.K. [Univ. of Crete (Greece)

    1997-12-31

    There is currently many ongoing investigations of the change in the glass transition temperature when a material is reduced in dimension from the normal bulk state. The reduction in dimension can be accomplished by casting the material as thin films with or without a substrate or putting it in nanometer size pores. In this work, the authors explore possible causes of the change in dynamics of the bulk material when the glass-former is subjected to such modifications. The existence of a growing cooperative length scale L(T) with decreasing temperature in bulk fragile glass-forming liquids reaching the size of approximately 1.5--2.0 nm at the glass transition temperature is the basis of the consideration. When the reduced dimension is comparable to L(T{sub g}), cooperative dynamics within a length scale equal to L(T{sub g}) can no longer be maintained in all three dimensions throughout the sample. The imposed reduction of the cooperative length scale speeds up the dynamics and causes a reduction of the glass transition temperature. For polymeric glass-formers particularly at higher molecular weights, reduction of one dimension in thin films engenders orientation of the polymer chains when their radius of gyration becomes comparable to the film thickness. The latter is known to cause also a reduction of the glass transition temperature.

  12. Method of forming crystalline silicon devices on glass

    Science.gov (United States)

    McCarthy, A.M.

    1995-03-21

    A method is disclosed for fabricating single-crystal silicon microelectronic components on a silicon substrate and transferring same to a glass substrate. This is achieved by utilizing conventional silicon processing techniques for fabricating components of electronic circuits and devices on bulk silicon, wherein a bulk silicon surface is prepared with epitaxial layers prior to the conventional processing. The silicon substrate is bonded to a glass substrate and the bulk silicon is removed leaving the components intact on the glass substrate surface. Subsequent standard processing completes the device and circuit manufacturing. This invention is useful in applications requiring a transparent or insulating substrate, particularly for display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard electronics, and high temperature electronics. 7 figures.

  13. Glass binder development for a glass-bonded sodalite ceramic waste form

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Brian J.; Vienna, John D.; Frank, Steven M.; Kroll, Jared O.; Peterson, Jacob A.; Canfield, Nathan L.; Zhu, Zihua; Zhang, Jiandong; Kruska, Karen; Schreiber, Daniel K.; Crum, Jarrod V.

    2017-06-01

    This paper discusses work to develop Na2O-B2O3-SiO2 glass binders for immobilizing LiCl-KCl eutectic salt waste in a glass-bonded sodalite waste form following electrochemical reprocessing of used metallic nuclear fuel. Here, five new glasses with high Na2O contents were designed to generate waste forms having higher sodalite contents and fewer stress fractures. The structural, mechanical, and thermal properties of the new glasses were measured using variety of analytical techniques. The glasses were then used to produce ceramic waste forms with surrogate salt waste. The materials made using the glasses developed during this study were formulated to generate more sodalite than materials made with previous baseline glasses used. The coefficients of thermal expansion for the glass phase in the glass-bonded sodalite waste forms made with the new binder glasses were closer to the sodalite phase in the critical temperature region near and below the glass transition temperature. These improvements should result in lower probability of cracking in the full-scale monolithic ceramic waste form, leading to better long-term chemical durability. Additionally, a model generated during this study for predicting softening temperature of silicate binder glasses is presented.

  14. Numerical study of pile-up in bulk metallic glass during spherical indentation

    Institute of Scientific and Technical Information of China (English)

    Al Ke; DAI LanHong

    2008-01-01

    Pile-up around indenter is usually observed during instrumented indentation tests on bulk metallic glass. Neglecting the pile-up effect may lead to errors in evaluating hardness, Young's modulus, stress-strain response, etc. Finite element analysis was employed to implement numerical simulation of spherical indentation tests on bulk metallic glass. A new model was proposed to describe the pile-up effect. By using this new model, the contact radius and hardness of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass were obtained under several different indenter loads with pile-up, and the results agree well with the data generated by numerical simulation.

  15. Numerical study of pile-up in bulk metallic glass during spherical indentation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Pile-up around indenter is usually observed during instrumented indentation tests on bulk metallic glass. Neglecting the pile-up effect may lead to errors in evaluating hardness,Young’s modulus,stress-strain response,etc. Finite element analysis was employed to implement numerical simulation of spherical indentation tests on bulk metallic glass. A new model was proposed to describe the pile-up effect. By using this new model,the contact radius and hardness of Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass were obtained under several different indenter loads with pile-up,and the results agree well with the data generated by numerical simulation.

  16. Glass transition and crystallization process of hard magnetic bulk Nd60Al10Fe20Co10 metallic glass

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Glass transition and crystallization process of bulk Nd60Al10Fe20Co10 metallic glass were investigated by means of dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electronic microscopy (SEM). It is shown that the glass transition and onset crystallization temperature determined by DMTA at a heating rate of 0.167 K/s are 480 and 588 K respectively. The crystallization process of the metallic glass is concluded as follows: amorphous α→α′+metastable FeNdAl novel phase →α′+primary δ phase→primary δ phase+eutectic δ phase Nd3Al phase+Nd3Co phase. The appearance of hard magnetism in this alloy is ascribed to the presence of amorphous phase with highly relaxed structure. The hard magnetism disappeared after the eutectic crystallization of amorphous phase.

  17. Transitions of amorphous- crystalline-amorphous in bulk metallic glass under HP and HT

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In-situ SR-XRD measurements revealed that the crystallization process in Zr41.2Ti13.sCu12.5Ni10Be22.5 bulk metallic glass is significantly different from that in traditional glasses. Subsequent heating at 10 GPa converts the sample from amorphous phase into the metastable fcc phase and then leads to the fcc phase back to the amorphous phase,nomena in the material under high pressure and high temperature.``

  18. Wear Behavior of Mechanically Alloyed Ti-Based Bulk Metallic Glass Composites Containing Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Yung-Sheng Lin

    2016-11-01

    Full Text Available The present paper reports the preparation and wear behavior of mechanically alloyed Ti-based bulk metallic glass composites containing carbon nanotube (CNT particles. The differential scanning calorimeter results show that the thermal stability of the amorphous matrix is affected by the presence of CNT particles. Changes in glass transition temperature (Tg and crystallization temperature (Tx suggest that deviations in the chemical composition of the amorphous matrix occurred because of a partial dissolution of the CNT species into the amorphous phase. Although the hardness of CNT/Ti50Cu28Ni15Sn7 bulk metallic glass composites is increased with the addition of CNT particles, the wear resistance of such composites is not directly proportional to their hardness, and does not follow the standard wear law. A worn surface under a high applied load shows that the 12 vol. % CNT/Ti50Cu28Ni15Sn7 bulk metallic glass composite suffers severe wear compared with monolithic Ti50Cu28Ni15Sn7 bulk metallic glass.

  19. Size effect on beta relaxation in a La-based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Wei; Wu, Jili, E-mail: wujili@msn.com; Zhang, Bo, E-mail: bo.zhang@hfut.edu.cn

    2017-03-15

    This work studied the effect of the size of specimens on the β relaxation. Taking La{sub 70}Ni{sub 15}Al{sub 15} bulk metallic glass as a model material, via dynamic mechanical analysis, we found that the thickness of specimens can affect the intensity of β relaxation. Specifically, increasing the thickness of specimens can enhance intensity of β relaxation. For this enhancement, we proposed that the involvedly total free volume facilitates the β relaxed process. This finding gives a new insight on the structural relaxation of bulk metallic glasses, especially for understanding of origin of β relaxation.

  20. Size effect on beta relaxation in a La-based bulk metallic glass

    Science.gov (United States)

    Jiang, Wei; Wu, Jili; Zhang, Bo

    2017-03-01

    This work studied the effect of the size of specimens on the β relaxation. Taking La70Ni15Al15 bulk metallic glass as a model material, via dynamic mechanical analysis, we found that the thickness of specimens can affect the intensity of β relaxation. Specifically, increasing the thickness of specimens can enhance intensity of β relaxation. For this enhancement, we proposed that the involvedly total free volume facilitates the β relaxed process. This finding gives a new insight on the structural relaxation of bulk metallic glasses, especially for understanding of origin of β relaxation.

  1. Shear bands in a bulk metallic glass after large plastic deformation

    Energy Technology Data Exchange (ETDEWEB)

    Qu, D.D.; Wang, Y.B.; Liao, X.Z.; Shen, J. (Harbin); (Sydney)

    2012-10-23

    A transmission electron microscopy investigation is conducted to trace shear bands in a Zr{sub 53}Cu{sub 18.7}Ni{sub 12}Al{sub 16.3} bulk metallic glass after experiencing 4% plastic deformation. Shear band initiation, secondary shear band interactions, mature shear band broadening and the interactions of shear bands with shear-induced nanocrystals are captured. Results suggest that the plasticity of the bulk metallic glass is enhanced by complex shear bands and their interactions which accommodate large plastic strain and prevent catastrophic shear band propagation.

  2. Looking for footprint of bulk metallic glass in electronic and phonon heat capacities of Cu55Hf45-xTix alloys

    Science.gov (United States)

    Remenyi, G.; Biljaković, K.; Starešinić, D.; Dominko, D.; Ristić, R.; Babić, E.; Figueroa, I. A.; Davies, H. A.

    2014-04-01

    We report on the heat capacity investigation of Cu55Hf45-xTix metallic glasses. The most appropriate procedure to estimate low temperature electronic and phonon contributions has been determined. Both contributions exhibit monotonous Ti concentration dependence, demonstrating that there is no relation of either the electron density of states at the Fermi level or the Debye temperature to the increased glass forming ability in the Ti concentration range x = 15-30. The thermodynamic parameters (e.g., reduced glass temperature) remain better indicators in assessing the best composition for bulk metallic glass formation.

  3. Feed Variability and Bulk Vitrification Glass Performance Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Mahoney, Lenna A.; Vienna, John D.

    2005-01-10

    The supplemental treatment (ST) bulk vitrification process will obtain its feed, consisting of low-activity waste (LAW), from more than one source. One purpose of this letter report is to describe the compositional variability of the feed to ST. The other is to support the M-62-08 decision by providing a preliminary assessment of the effectiveness of bulk vitrification (BV), the process that has been selected to perform supplemental treatment, in handling the ST feed envelope. Roughly nine-tenths of the ST LAW feed will come from the Waste Treatment Plant (WTP) pretreatment. This processed waste is expected to combine (1) a portion of the same LAW feed sent to the WTP melters and (2) a dilute stream that is the product of the condensate from the submerged-bed scrubber (SBS) and the drainage from the electrostatic precipitator (WESP), both of which are part of the LAW off-gas system. The manner in which the off-gas-product stream is concentrated to reduce its volume, and the way in which the excess LAW and off-gas product streams are combined, are part of the interface between WTP and ST and have not been determined. This letter report considers only one possible arrangement, in which half of the total LAW is added to the off-gas product stream, giving an estimated ST feed stream from WTP. (Total LAW equals that portion of LAW sent to the WTP LAW vitrification plant (WTP LAW) plus the LAW not currently treatable in the LAW vitrification plant due to capacity limitations (excess)).

  4. Mid-infrared emission from Dy3+ doped tellurite bulk glass and waveguides

    Science.gov (United States)

    Richards, Billy D. O.; Teddy-Fernandez, Toney; Jha, Animesh; Binks, David

    2012-11-01

    We present the fabrication and characterisation of Dy3+-doped tellurite glasses and waveguides for applications in the mid-IR. The low phonon energy and large rare-earth ion solubility of tellurite glasses, as well as having infrared transmission ranges up to glasses, glass characterisation and rare-earth ion spectroscopy which is compared to other glass hosts relevant to the mid-IR such as fluoride glasses. When excited with an 808 nm laser diode source, Dy3+ doped tellurite bulk glasses exhibited very broad fluorescence from the 6H13/2 - 6H15/2 transition which extends from 3 μm to 3.6 μm FWHM compared to 2.9 μm to 3.1 μm in Dy3+ doped ZBLAN glass. This broad and red-shifted fluorescence band in tellurite glass may find use in LIDAR and sensing applications as it coincides with an atmospheric transmission band, compared to the ~3 μm emission of Dy3+ doped ZBLAN lasers which is absorbed by atmospheric water.

  5. Advanced Wear Simulation for Bulk Metal Forming Processes

    Directory of Open Access Journals (Sweden)

    Behrens Bernd-Arno

    2016-01-01

    Full Text Available In the recent decades the finite element method has become an essential tool for the cost-efficient virtual process design in the metal forming sector in order to counter the constantly increasing quality standards, particularly from the automotive industry as well as intensified international competition in the forging industry. An optimized process design taking precise tool wear prediction into account is a way to increase the cost-efficiency of the bulk metal forming processes. The main objective of the work presented in this paper is a modelling algorithm, which allows predicting die wear with respect to a geometry update during the forming simulation. Changes in the contact area caused by geometry update lead to the different die wear distribution. It primarily concerns the die areas, which undergo high thermal and mechanical loads.

  6. An interatomic potential for studying CuZr bulk metallic glasses

    DEFF Research Database (Denmark)

    Paduraru, Anca; Kenoufi, Abdel; Bailey, Nicholas

    2007-01-01

    -scale deformation events and may furthermore involve localization through formation of shear bands. In this paper, an Effective Medium Theory (EMT) potential optimized for modeling the mechanical and thermodynamic properties of CuZr bulk metallic glass is studied. The late transition metals crystallizing in close...

  7. Compressive Deformation Induced Nanocrystallization of a Supercooled Zr-Based Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    GUO Xiao-Lin; SHAN De-Bin; MA Ming-Zhen; GUO Bin

    2008-01-01

    The nanocrystallization behaviour of a bulk Zr-based metallic glass subjected to compressive stress is investigated in the supercooled liquid region. Compared with annealing treatments without compressive stress, compressive deformation promotes the development of nucleation and suppresses the coarsening of nanocrystallites at high ternperatures.

  8. Magnetic properties of Fe-Co-based bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Tiberto, Paola, E-mail: tiberto@inrim.i [INRIM, Electromagnetism Division, Strada delle Cacce 91, I-10135 Torino (Italy); Piccin, Rafael [Universita di Torino, Dipartimento di Chimica IFM and NIS, I-10125 Torino (Italy); Lupu, Nicoleta; Chiriac, Horia [National Institute of Research and Development for Technichal Physics, 700050 Iasi (Romania); Baricco, Marcello [Universita di Torino, Dipartimento di Chimica IFM and NIS, I-10125 Torino (Italy)

    2009-08-26

    Amorphous [(Fe{sub 1-x}Co{sub x}){sub 75}B{sub 20}Si{sub 5}]{sub 93}Nb{sub 4}Y{sub 3}(x=0, 0.2 and 0.4) have been produced by water-cooled Cu-mold injection casting technique in cylindrical shape. Amorphous ribbon having the same composition have been produced by rapid quenching technique. The presence of an amorphous structure have been checked by means of X-ray diffraction measurements and differential scanning calorimetry. Magnetic hysteresis loops have been measured by means of vibrating sample magnetometer at a maximum field of 10 kOe. In addition, to study the frequency dependence of magnetic losses, hysteresis loops have been measured by a digital wattmeter. A critical analysis of the results obtained on both ribbons and bulk cylinder will be presented. The obtained data will be compared with the ones of Fe-based materials conventionally exploited in applications.

  9. Structure and properties of Fe-Cr-Mo-C bulk metallic glasses obtained by die casting method

    Directory of Open Access Journals (Sweden)

    W. Pilarczyk

    2010-09-01

    Full Text Available urpose: The goal of this work is to investigate structure and properties of Fe54Cr16Mo12C18 alloy rods with different diameters obtained by the pressure die casting method.Design/methodology/approach: Master alloy ingot with compositions of Fe54Cr16Mo12C18 was prepared by induction melting of pure Fe, Cr, Mo, C elements in argon atmosphere. The investigated material were cast in form of rods with different diameters. Glassy and crystalline structures were examined by X-ray diffraction. The microscopic observation of the fracture morphology was carried out by the SEM with different magnification. The thermal properties of the studied alloy were examined by DTA and DSC method.Findings: These materials exhibit high glass-forming ability, excellent mechanical properties and corrosion resistance.Research limitations/implications: It is difficult to obtain a metallic glass of Fe54Cr16Mo12C18 alloy. The investigations carried out on the different samples of Fe54Cr16Mo12C18 bulk metallic alloy allowed to state that the studied ribbon was amorphous whereas rods were amorphous – crystalline.Originality/value: The formation and investigation of the casted Fe-Cr-Mo-C bulk materials and the study of glass-forming ability of this alloy.

  10. Magnetocaloric effect in heavy rare-earth elements doped Fe-based bulk metallic glasses with tunable Curie temperature

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jiawei; Huo, Juntao; Chang, Chuntao, E-mail: ctchang@nimte.ac.cn, E-mail: dujun@nimte.ac.cn; Du, Juan, E-mail: ctchang@nimte.ac.cn, E-mail: dujun@nimte.ac.cn; Man, Qikui; Wang, Xinmin; Li, Run-Wei [Key Laboratory of Magnetic Materials and Devices, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Law, Jiayan [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden)

    2014-08-14

    The effects of heavy rare earth (RE) additions on the Curie temperature (T{sub C}) and magnetocaloric effect of the Fe-RE-B-Nb (RE = Gd, Dy and Ho) bulk metallic glasses were studied. The type of dopping RE element and its concentration can easily tune T{sub C} in a large temperature range of 120 K without significantly decreasing the magnetic entropy change (ΔS{sub M}) and refrigerant capacity (RC) of the alloys. The observed values of ΔS{sub M} and RC of these alloys compare favorably with those of recently reported Fe-based metallic glasses with enhanced RC compared to Gd{sub 5}Ge{sub 1.9}Si{sub 2}Fe{sub 0.1}. The tunable T{sub C} and large glass-forming ability of these RE doped Fe-based bulk metallic glasses can be used in a wide temperature range with the final required shapes.

  11. Estimation of Gibbs free energy difference in Pd-based bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    Cai Anhui; Xiong Xiang; Liu Yong; Tan JingYing; Zhou Yong; An Weike

    2008-01-01

    A new thermodynamic expression for Gibbs free energy difference 4G between the under-cooled Iiquid and the corresponding crystals of bulk metallic glasses was derived.The newly proposed expression always gives results in fairly good agreement with experimental values over entire temperature range between the fusion temperature Tm and the glass transition temperature Tg of Pd40Ni40P20,Pd40Cu30Ni10P20 and Pd43Cu27Ni10P20,which possess different heat capacities.However,the TS and KN expressions cannot always provide results in good agreement with the experimental values.In addition.the deviations between the experimental values and the △G calculated by the proposed expression at Tg are smaller than those given by other expressions for all the bulk metallic glasses studied.

  12. POLYMER CHAIN DIFFUSION AT A TEMPERATURE BELOW ITS BULK GLASS TRANSITION TEMPERATURE

    Institute of Scientific and Technical Information of China (English)

    Tisato Kajiyama; Daisuke Kawaguchi; Keiji Tanaka

    2003-01-01

    In this study, it was examined whether the dynamics of polymer chains at a surface is different from that in the bulk, and if so, to what extent they differ in terms of surface glass transition temperature and diffusion coefficient. Obtained results clearly indicate that surface chains can travel for a relatively large distance in comparison with the characteristic length scale of usual segmental motion even at a temperature below its bulk glass transition temperature, Tbg. This is consistent with our previous results that the surface glass transition temperature is much lower than the corresponding Tbg.Also, it was experimentally revealed that there was a gradient of molecular motion in the surface region.

  13. Integrated thermomechanical model for forming of glass containers

    Directory of Open Access Journals (Sweden)

    Martins Bruno

    2016-01-01

    Full Text Available In this work an integrated model for all the process of glass forming of glass containers is presented. The model addresses press-and-blow and blow-and-blow procedures from the gob forming to the final product. Glass forming involves coupled thermal-mechanical physical phenomena, in which the material viscous flow is highly dependent on heat transfer which, in turn, is dependent changes of shape due to material flow. Numerical aspects associated with the model implementation and its validation with real formed products are discussed.

  14. Naturally occurring glasses: analogues for radioactive waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, R.C.; Haaker, R.F.

    1979-04-01

    Volcanic glasses are very often altered by weathering and leaching and recrystallize to their fine-grained equivalents (rhyolites, felsites). The oldest volcanic glasses are dated at 40 million years before the present, but the majority are much younger. Devitrification textures was produced experimentally; and hydration rates for volcanic glasses were determined as a function of composition, temperature, and climate. Presence of water and temperature are the most important rate controlling variables. Even material that may still be described as glassy often exhibits evidence of alteration and recrystallization. Of the volcanic glasses that are preserved in the geologic record, it would be rare to describe such a glass as pristine. Despite the common alteration and recrystallization effects observed in volcanic glasses, glasses formed as a result of impact, tektites and lunar glasses, may occur in substantially unaltered form. In the case of tektites, their resistance to alteration is a result of their high SiO/sub 2/ content and low alkali content. Lunar glasses have been preserved for hundreds of millions of years because they exist in an environment with a low oxygen fugacity and an extremely low water vapor partial presssure. Thus one might expect glasses of particular compositions or in specific types of environment to be stable for long periods of time. These conclusions are applied to radioactive waste disposal over several time periods (0-30h, 30h-20y, 20-200y).

  15. Naturally occurring glasses: analogues for radioactive waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, R.C.; Haaker, R.F.

    1979-04-01

    Volcanic glasses are very often altered by weathering and leaching and recrystallize to their fine-grained equivalents (rhyolites, felsites). The oldest volcanic glasses are dated at 40 million years before the present, but the majority are much younger. Devitrification textures was produced experimentally; and hydration rates for volcanic glasses were determined as a function of composition, temperature, and climate. Presence of water and temperature are the most important rate controlling variables. Even material that may still be described as glassy often exhibits evidence of alteration and recrystallization. Of the volcanic glasses that are preserved in the geologic record, it would be rare to describe such a glass as pristine. Despite the common alteration and recrystallization effects observed in volcanic glasses, glasses formed as a result of impact, tektites and lunar glasses, may occur in substantially unaltered form. In the case of tektites, their resistance to alteration is a result of their high SiO/sub 2/ content and low alkali content. Lunar glasses have been preserved for hundreds of millions of years because they exist in an environment with a low oxygen fugacity and an extremely low water vapor partial presssure. Thus one might expect glasses of particular compositions or in specific types of environment to be stable for long periods of time. These conclusions are applied to radioactive waste disposal over several time periods (0-30h, 30h-20y, 20-200y).

  16. Sheet-bulk metal formingforming of functional components from sheet metals

    Directory of Open Access Journals (Sweden)

    Merklein Marion

    2015-01-01

    Full Text Available The paper gives an overview on the application of sheet-bulk metal forming operations in both scientific and industrial environment. Beginning with the need for an innovative forming technology, the definition of this new process class is introduced. The rising challenges of the application of bulk metal forming operations on sheet metals are presented and the demand on a holistic investigation of this topic is motivated. With the help of examples from established production processes, the latest state of technology and the lack on fundamental knowledge is shown. Furthermore, perspectives regarding new research topics within sheet-bulk metal forming are presented. These focus on processing strategies to improve the quality of functional components by the application of process-adapted semi-finished products as well as the local adaption of the tribological system.

  17. Simulation of sheet-bulk metal forming processes with simufact.forming using user-subroutines

    Science.gov (United States)

    Beese, Steffen; Beyer, Florian; Blum, Heribert; Isik, Kerim; Kumor, Dustin; Löhnert, Stefan; Rademacher, Andreas; Tekkaya, A. Erman; Willner, Kai; Wriggers, Peter; Zeller, Sebastian

    2016-10-01

    In this article, we consider the simulation of sheet-bulk metal forming processes, which makes high demands on the underlying models and on the simulation software. We present our approach to incorporate new modelling approaches from various fields in a commercial simulation software, in our case Simufact.forming. Here, we discuss material, damage, and friction models as well as model adaptive techniques.

  18. Spectrophotometric determination of nateglinide in bulk and tablet dosage forms

    Directory of Open Access Journals (Sweden)

    Jain Suresh

    2009-01-01

    Full Text Available Nateglinide (NTG is available as tablet dosage form in 60 mg and 120 mg strength. In the present study, two simple, reproducible and efficient UV spectrophotometric methods for the estimation of this drug in bulk and pharmaceutical dosage forms have been developed. In method I, methanol-AR was used as solvent, while in method II, Methanol-AR + 10% V/V 3N NaOH was used as reference solvent. In method I, nateglinide shows λmax at 216 nm, which is then shifted to 225.4 nm on increasing the basicity of the reference solvent in method II. The linearity for nateglinide was observed to be statistically in the range of 10-100 μg/ml in method I and 100-1000 μg/ml in method II. Both the methods were validated using ANOVA. The recovery studies confirmed the accuracy of the proposed methods.

  19. Simulation study of mechanical properties of bulk metallic glass systems: martensitic inclusions and twinned precipitates

    Science.gov (United States)

    Zaheri, A.; Abdeljawad, F.; Haataja, M.

    2014-12-01

    Monolithic bulk metallic glasses (BMGs) exhibit a unique combination of mechanical properties, such as high strength and large elasticity limits, but the lack of ductility is considered the main Achilles' heel of BMG systems. To increase the competitiveness of BMGs vis-à-vis conventional structural materials, the problem of catastrophic failure via intense plastic strain localization (‘shear banding’) has to be addressed. Recent experimental observations suggest that the addition of structural heterogeneities, in the form of crystalline particles, to BMG systems hinders the catastrophic propagation of shear bands and leads to enhanced ductility. These structural heterogeneities can be introduced by either forming BMG composites, where second-phase crystalline particles accommodate applied loads via martensitic transformation mechanisms, or developing glassy alloys that precipitate crystalline particles under deformation, a process by which further deformation can be sustained by twinning mechanisms in the crystalline phase. In this work, we present a non-linear continuum model capable of capturing the structural heterogeneity in the glassy phase and accounting for intrinsic work hardening via martensitic transformations in second-phase reinforcements in BMG composites and deformation twinning in precipitated crystalline particles. Simulation results reveal that in addition to intrinsic work hardening in the crystalline phase, particle size greatly affects the overall mechanical behavior of these BMG systems. The precipitation of crystalline particles in monolithic BMGs yields two-phase microstructures that promote more homogeneous deformation, delay the propagation of incipient shear bands, and ultimately result in improved ductility characteristics.

  20. Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses

    Science.gov (United States)

    Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer; Thorpe, Steven John

    2015-09-01

    Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal-transition metal and transition metal-metalloid (TM-M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM-M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator.

  1. Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses.

    Science.gov (United States)

    Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer; Thorpe, Steven John

    2015-09-21

    Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal-transition metal and transition metal-metalloid (TM-M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM-M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator.

  2. Investigating the atomic level influencing factors of glass forming ability in NiAl and CuZr metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Sedighi, Sina; Kirk, Donald Walter; Singh, Chandra Veer, E-mail: chandraveer.singh@utoronto.ca; Thorpe, Steven John [Department of Materials Science and Engineering, University of Toronto, Room 140, 184 College Street, Toronto, Ontario M5S 3E4 (Canada)

    2015-09-21

    Bulk metallic glasses are a relatively new class of amorphous metal alloy which possess unique mechanical and magnetic properties. The specific concentrations and combinations of alloy elements needed to prevent crystallization during melt quenching remains poorly understood. A correlation between atomic properties that can explain some of the previously identified glass forming ability (GFA) anomalies of the NiAl and CuZr systems has been identified, with these findings likely extensible to other transition metal–transition metal and transition metal–metalloid (TM–M) alloy classes as a whole. In this work, molecular dynamics simulation methods are utilized to study thermodynamic, kinetic, and structural properties of equiatomic CuZr and NiAl metallic glasses in an attempt to further understand the underlying connections between glass forming ability, nature of atomic level bonding, short and medium range ordering, and the evolution of structure and relaxation properties in the disordered phase. The anomalous breakdown of the fragility parameter as a useful GFA indicator in TM–M alloy systems is addressed through an in-depth investigation of bulk stiffness properties and the evolution of (pseudo)Gruneisen parameters over the quench domain, with the efficacy of other common glass forming ability indicators similarly being analyzed through direct computation in respective CuZr and NiAl systems. Comparison of fractional liquid-crystal density differences in the two systems revealed 2-3 times higher values for the NiAl system, providing further support for its efficacy as a general purpose GFA indicator.

  3. Compressive behavior of bulk metallic glass under different conditions --- Coupled effect of temperature and strain rate

    Science.gov (United States)

    Yin, Weihua

    Metallic glass was first reported in 1960 by rapid quenching of Au-Si alloys. But, due to the size limitation, this material did not attract remarkable interest until the development of bulk metallic glasses (BMGs) with specimen sizes in excess of 1 mm. BMGs are considered to be promising engineering materials because of their ultrahigh strength, high elastic limit and wear resistance. However, they usually suer from a strong tendency for localized plastic deformation with catastrophic failure. Many basic questions, such as the origin of shear softening and the strain rate eect remain unclear. In this thesis, the mechanical behavior of the Zr55Al 10Ni5Cu30 bulk metallic glass and a metallic glass composite is investigated. The stress-strain relationship for Zr55Al10Ni 5Cu30 over a wide range of strain rate (5x10 --5 to 2x103 s--1) was investigated in uniaxial compression loading using both MTS servo-hydraulic system (quasi-static) and compression Kolsky bar system (dynamic). The effect of the strain rate on the fracture stress at room temperature was discussed. Based on the experimental results, the strain rate sensitivity of the bulk metallic glass changes from a positive value to a negative value at high strain rate, which is a consequence of the significant adiabatic temperature rise during the dynamic testing. In order to characterize the temperature eect on the mechanical behavior of the metallic glass, a synchronically assembled heating unit was designed to be attached onto the Kolsky bar system to perform high temperature and high strain rate mechanical testing. A transition from inhomogeneous deformation to homogeneous deformation has been observed during the quasi-static compressive experiments at testing temperatures close to the glass transition temperature. However, no transition has been observed at high strain rates at all the testing temperatures. A free volume based model is applied to analyze the stress-strain behavior of the homogeneous

  4. Effect of Au Content on Thermal Stability and Mechanical Properties of Au-Cu-Ag-Si Bulk Metallic Glasses

    Science.gov (United States)

    Guo, H.; Zhang, W.; Chen, M. W.; Saotome, Y.; Fukuhara, M.; Inoue, A.

    2011-06-01

    The thermal stability, glass-forming ability (GFA), and mechanical and electrical properties of Au-based Au x Si17Cu75.5- x Ag7.5 ( x = 40 to 75.5 at. pct) metallic glasses were investigated. The glass transition temperature ( T g ) and crystallization temperature ( T x ) decreased with increasing Au content. The ultralow T g values below 373 K (100 °C) were obtained for alloys with x = 55 to 75.5. The alloys with x = 45 to 70 exhibited a high stabilization of supercooled liquid and a high GFA, and the supercooled liquid region and critical sample diameter for glass formation were in the range of 31 K to 50 K and 2 to 5 mm, respectively. The compressive fracture strength ( σ c,f ), Young's modulus ( E), and Vicker's hardness ( H v ) of the bulk metallic glasses (BMGs) decreased with increasing Au content. A linear correlation between Au concentration and the characteristic temperature, i.e., T g and T x , and mechanical properties, i.e., σ c,f , E, and H v , as well as electrical resistivity can be found in the BMGs, which will be helpful for the composition design of the desirable Au-based BMGs with tunable physical properties.

  5. Development of Fe-B Based Bulk Metallic Glasses: Morphology of Residual Phases in Fe50Ni16Mo6B18Zr10 Glass

    Directory of Open Access Journals (Sweden)

    Tiburce A. Aboki

    2013-04-01

    Full Text Available Iron-boron based bulk metallic glasses (BMG development has been initiated using Fe40Ni38Mo4B18 as precursor. Addition of zirconium up to 10 atomic % along with the reduction of Ni proportion improves the glass forming ability (GFA, which is optimum when Ni is suppressed in the alloy. However melting instability occurred during the materials fabrication resulting in the formation of residual crystalline phases closely related to the amorphous phase. Microstructure study shows an evolution from amorphous structure to peculiar acicular structure, particularly for Fe50Ni16Mo6B18Zr10, suggesting the amorphous structure as interconnected atomic sheets like “atomic mille feuilles” whose growth affects the alloys’ GFA.

  6. The fluidity and molding ability of glass-forming Zr-based alloy melt

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The fluidity and filling ability of glass-forming Zr-based alloy melt in copper mould were investigated both theoretically and experimentally. The major factors which affected the flowing behavior of the metallic melt in the mold were determined,which provides the foundation for overcoming the contradiction between the filling and formation of amorphous alloy during the rapid cooling process of the metallic melts. The casting factors to prepare a metallic ring were discussed and selected. As a result,a Zr-based bulk metallic glass ring was prepared successfully.

  7. Deformation-Induced Martensitic Transformation in Cu-Zr-Zn Bulk Metallic Glass Composites

    Directory of Open Access Journals (Sweden)

    Dianyu Wu

    2015-11-01

    Full Text Available The microstructures and mechanical properties of (Cu0.5Zr0.5100−xZnx (x = 0, 1.5, 2.5, 4.5, 7, 10, and 14 at. % bulk metallic glass (BMG composites were studied. CuZr martensitic crystals together with minor B2 CuZr and amorphous phases dominate the microstructures of the as-quenched samples with low Zn additions (x = 0, 1.5, and 2.5 at. %, while B2 CuZr and amorphous phases being accompanied with minor martensitic crystals form at a higher Zn content (x = 4.5, 7, 10, and 14 at. %. The fabricated Cu-Zr-Zn BMG composites exhibit macroscopically appreciable compressive plastic strain and obvious work-hardening due to the formation of multiple shear bands and the deformation-induced martensitic transformation (MT within B2 crystals. The present BMG composites could be a good candidate as high-performance structural materials.

  8. An Assessment of Binary Metallic Glasses: Correlations Between Structure, Glass Forming Ability and Stability (Preprint)

    Science.gov (United States)

    2011-07-01

    release; distribution unlimited. 1. Introduction It has long been suggested that metallic glass stability and glass-forming ability (GFA) are... magnetostriction of Co-Cr-Zr amorphous alloys’, Rapidly Quenched Metals, Proc. 4th International Conference on Rapidly Quenched Metals, Sendai, Japan, 861-864

  9. Effect of Aluminium Addition on Glass Forming Ability of Nd55-xAl10+xFe15Co20 (x=0, 5, 10) Alloys

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Nd55-xAl10+xCo20Fe15 (x=0, 5, 10) bulk glass-forming alloys with distinct glass transition in differential scanning calorimetry (DSC) traces were obtained by suction casting. The glass forming ability (GFA) of the alloys was investigated. It was found that the reduced glass transition temperature (Trg) and the parameter γ of the alloys increased with the increasing concentration of Al. The glass formation enthalpy of the alloys was calculated based on Miedema′s model, and it was suggested that the GFA of the alloys could be enhanced by the decrease of the glass formation enthalpy with Al additions.

  10. Nanoscale physical properties of polymer glasses formed by solvent-assisted laser deposition

    Science.gov (United States)

    Shepard, Kimberly; Arnold, Craig; Priestley, Rodney

    2015-03-01

    High-energy, low-density nanostructured polymer glasses are formed via the solvent-assisted laser deposition technique MAPLE (Matrix Assisted Pulsed Laser Evaporation). During film deposition, micro- to nano-size polymer/solvent clusters are ejected via laser ablation from a frozen dilute polymer solution. During flight to the substrate under vacuum, the clusters experience rapid cooling and solvent stripping, forming polymer nanoglobules. Bulk polymer films are formed via the gradual assembly of these spherical-like nanostructured building blocks (i.e. nanoglobules). The MAPLE process thus enables investigation of the exceptional properties of glasses formed under extreme processing conditions. In the bulk state, we probe the effect of process parameters and chemical identity of the thermal behavior of a series of methacrylate polymers. We also employ multiple techniques to directly measure the properties of the polymer nanoglobules and connect the results to the global film properties. This talk will address nanoscale dilatometry via AFM, in which the volume of an individual polymer nanoglobule is tracked as it is heated through its glass transition, as well as Flash DSC analysis of the thermal properties of nanogram size MAPLE-deposited polymer glasses. We then discuss these findings in the context of the material's unconventional route to the glassy state.

  11. Crystallization dynamics in glass-forming systems

    Energy Technology Data Exchange (ETDEWEB)

    Cullinan, Timothy Edward [Iowa State Univ., Ames, IA (United States)

    2016-02-19

    Crystallization under far-from-equilibrium conditions is investigated for two different scenarios: crystallization of the metallic glass alloy Cu50Zr50 and solidification of a transparent organic compound, o-terphenyl. For Cu50Zr50, crystallization kinetics are quanti ed through a new procedure that directly fits thermal analysis data to the commonly utilized JMAK model. The phase evolution during crystallization is quantified through in-situ measurements (HEXRD, DSC) and ex-situ microstructural analysis (TEM, HRTEM). The influence of chemical partitioning, diffusion, and crystallographic orientation on this sequence are examined. For o-terphenyl, the relationship between crystal growth velocity and interface undercooling is systematically studied via directional solidification.

  12. Stress-Corrosion Interactions in Zr-Based Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Petre Flaviu Gostin

    2015-07-01

    Full Text Available Stress-corrosion interactions in materials may lead to early unpredictable catastrophic failure of structural parts, which can have dramatic effects. In Zr-based bulk metallic glasses, such interactions are particularly important as these have very high yield strength, limited ductility, and are relatively susceptible to localized corrosion in halide-containing aqueous environments. Relevant features of the mechanical and corrosion behavior of Zr-based bulk metallic glasses are described, and an account of knowledge regarding corrosion-deformation interactions gathered from ex situ experimental procedures is provided. Subsequently the literature on key phenomena including hydrogen damage, stress corrosion cracking, and corrosion fatigue is reviewed. Critical factors for such phenomena will be highlighted. The review also presents an outlook for the topic.

  13. Fabricating Zr-Based Bulk Metallic Glass Microcomponent by Suction Casting Using Silicon Micromold

    Directory of Open Access Journals (Sweden)

    Zhijing Zhu

    2014-08-01

    Full Text Available A suction casting process for fabricating Zr55Cu30Al10Ni5 bulk metallic glass microcomponent using silicon micromold has been studied. A complicated BMG microgear with 50 μm in module has been cast successfully. Observed by scanning electron microscopy and laser scanning confocal microscopy, we find that the cast microgear duplicates the silicon micromold including the microstructure on the surface. The amorphous state of the microgear is confirmed by transmission election microscopy. The nanoindentation hardness and elasticity modulus of the microgear reach 6.5 GPa and 94.5 GPa. The simulation and experimental results prove that the suction casting process with the silicon micromold is a promising one-step method to fabricate bulk metallic glass microcomponents with high performance for applications in microelectromechanical system.

  14. Deformation behavior of Zr-based bulk metallic glass and composite in the supercooled liquid region

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A Zr-based bulk metallic glass (BMG) with a composition of (Zr75Cu25)78.5Ta4Ni10Al7.5 and a bulk metallic glass matrix composite (BMGC) with a composition of (Zr75Cu25)74.5Ta8Ni10Al7.5 have been prepared by copper-mold casting. The compres-sive deformation behavior of the BMG and BMGC was investigated in the super-cooled region at different temperatures and various strain rates ranging from 8×10-4s-1 to 8×10-2s-1. It was found that both the strain rate and test temperature signifi-cantly affect the deformation behavior of the two alloys. The deformation follows Newtonian flow at low strain rates but non-Newtonian flow at high strain rates. The deformation mechanism for the two kinds of alloys was discussed in terms of the transition state theory.

  15. Enhanced Mechanical Properties of MgZnCa Bulk Metallic Glass Composites with Ti-Particle Dispersion

    Directory of Open Access Journals (Sweden)

    Pei Chun Wong

    2016-05-01

    Full Text Available Rod samples of Mg60Zn35Ca5 bulk metallic glass composites (BMGCs dispersed with Ti particles have been successfully fabricated via injection casting. The glass forming ability (GFA and the mechanical properties of these Mg-based BMGCs have been systematically investigated as a function of the volume fraction (Vf of Ti particles. The results showed that the compressive ductility increased with Vf. The mechanical performance of these BMGCs, with up to 5.4% compressive failure strain and 1187 MPa fracture strength at room temperature, can be obtained for the Mg-based BMGCs with 50 vol % Ti particles, suggesting that these dispersed Ti particles can absorb the energy of the crack propagations and can induce branches of the primary shear band into multiple secondary shear bands. It follows that further propagation of the shear band is blocked, enhancing the overall plasticity.

  16. Mare glasses from Apollo 17 - Constraints on the moon's bulk composition

    Science.gov (United States)

    Delano, J. W.; Lindsley, D. H.

    1983-01-01

    Two previously unreported varieties of mare volcanic glass have been discovered in Apollo 17 samples. Twenty-three chemical types of volcanic glass have now been analyzed from the six Apollo landing sites. These volcanic glasses, which may be samples of primary magmas derived from the differentiated lunar mantle, define two linear arrays that seem to reflect regional, if not global, regularities among the source regions of these melts. Additional systematics among these glasses have been used to estimate the bulk composition of the moon. The results suggest that the refractory lithophile elements are present at abundances of 1.7 x chondrites. The silicate portion of the moon appears to have a major-element composition similar to a volatile (Si, Na, K)-depleted, earth's upper mantle. The theory involving an earth-fission origin of the moon can be tested further through trace element analyses on the volcanic glasses, and through determination of the N/Ar-36 ratio and noble gas isotopes from primordial lunar gas trapped within vesicles associated with mare volcanic glass.

  17. Atomic interaction mechanism for designing the interface of W/Zr-based bulk metallic glass composites

    OpenAIRE

    Li, Z K; Fu, H. M.; Sha, P. F.; Zhu, Z. W.; A. M. Wang; Li, H.; Zhang, H. W.; Zhang, H. F.; Hu, Z. Q.

    2015-01-01

    The interaction between active element Zr and W damages the W fibers and the interface and decreases the mechanical properties, especially the tensile strength of the W fibers reinforced Zr-based bulk metallic glass composites (BMGCs). From the viewpoint of atomic interaction, the W-Zr interaction can be restrained by adding minor elements that have stronger interaction with W into the alloy. The calculation about atomic interaction energy indicates that Ta and Nb preferred to segregate on th...

  18. Deformation-strengthening during rolling Cu60Zr20Ti20 bulk metallic glass

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Hu, Yuyan

    2007-01-01

    Mechanical strength evolutions during rolling the Cu60Zr20Ti20 bulk metallic glass (BMG) at room temperature (RT) and cryogenic temperature (CT) have been investigated by measuring the microhardness. The hardness slightly increases during the initial rolling stage as a result of the gradually......-rolling. It is proposed that phase separation may be a more effective way to strengthen the BMG than the incorporation of the nanocrystallites with crystal defects....

  19. An approach to predict free surface fracture in bulk forming

    Science.gov (United States)

    Ragab, A. R.

    2006-04-01

    This work presents a unified approach to predict surface strains at failure in bulk forming processes. The approach does not deal with a specific process but rather with prescribed strain and stress paths. The material to be processed is assumed to possess an initial void volume fraction that grows and colaesces with straining, ending by fracture. The predictions are based on a formulation for voided solids according to the Gurson-Tvergaard yield function adapted to include orthotropic anisotropy. The incident of fracture is characterized by shear band formation within the ligaments of the matrix material among spheroidal voids as described by McClintock. The results are represented by a straight line plot of tensile limit strain versus the compressive strain for different loading paths. These limit curves are shown to be dependent on the initial void fraction, hardening, and anisotropy of the matrix matrial. Alloys with lower initial void fractions as well as those of higher hardening show better workability. The model is applied to predict bulk formability curves for steels AISI 1040 and 1045, Aluminum AI 7075-T6, and copper, based on the proper selection of micromechanical parameters for these alloys. The validity of the model is ensured through fairly favorable comparison with experimentally determined limit curves. The current failure conditions are suitable to predict the experimental dual slope fracture line that may exist for some alloys such as cold-drawn steel AISI 1045 and aluminum 2024-T6 by considering two mechanisms of failure: internal necking in the ligament material between voids, followed by transition to shear band formation.

  20. Relationship between topological order and glass forming ability in densely packed enstatite and forsterite composition glasses.

    Science.gov (United States)

    Kohara, S; Akola, J; Morita, H; Suzuya, K; Weber, J K R; Wilding, M C; Benmore, C J

    2011-09-06

    The atomic structures of magnesium silicate melts are key to understanding processes related to the evolution of the Earth's mantle and represent precursors to the formation of most igneous rocks. Magnesium silicate compositions also represent a major component of many glass ceramics, and depending on their composition can span the entire fragility range of glass formation. The silica rich enstatite (MgSiO(3)) composition is a good glass former, whereas the forsterite (Mg(2)SiO(4)) composition is at the limit of glass formation. Here, the structure of MgSiO(3) and Mg(2)SiO(4) composition glasses obtained from levitated liquids have been modeled using Reverse Monte Carlo fits to diffraction data and by density functional theory. A ring statistics analysis suggests that the lower glass forming ability of the Mg(2)SiO(4) glass is associated with a topologically ordered and very narrow ring distribution. The MgO(x) polyhedra have a variety of irregular shapes in MgSiO(3) and Mg(2)SiO(4) glasses and a cavity analysis demonstrates that both glasses have almost no free volume due to a large contribution from edge sharing of MgO(x)-MgO(x) polyhedra. It is found that while the atomic volume of Mg cations in the glasses increases compared to that of the crystalline phases, the number of Mg-O contacts is reduced, although the effective chemical interaction of Mg(2+) remains similar. This unusual structure-property relation of Mg(2)SiO(4) glass demonstrates that by using containerless processing it may be possible to synthesize new families of dense glasses and glass ceramics with zero porosity.

  1. Mechanical relaxation in a Zr-based bulk metallic glass: Analysis based on physical models

    Science.gov (United States)

    Qiao, J. C.; Pelletier, J. M.

    2012-08-01

    The mechanical relaxation behavior in a Zr55Cu30Ni5Al10 bulk metallic glass is investigated by dynamic mechanical analysis in both temperature and frequency domains. Master curves can be obtained for the storage modulus G' and for the loss modulus G'', confirming the validity of the time-temperature superposition principle. Different models are discussed to describe the main (α) relaxation, e.g., Debye model, Havriliak-Negami (HN) model, Kohlrausch-Williams-Watt (KWW) model, and quasi-point defects (QPDs) model. The main relaxation in bulk metallic glass cannot be described using a single relaxation time. The HN model, the KWW model, and the QPD theory can be used to fit the data of mechanical spectroscopy experiments. However, unlike the HN model and the KWW model, some physical parameters are introduced in QPD model, i.e., atomic mobility and correlation factor, giving, therefore, a new physical approach to understand the mechanical relaxation in bulk metallic glasses.

  2. Experimental approach for thermal parameters estimation during glass forming process

    Science.gov (United States)

    Abdulhay, B.; Bourouga, B.; Alzetto, F.; Challita, C.

    2016-10-01

    In this paper, an experimental device designed and developedto estimate thermal conditions at the Glass / piston contact interface is presented. This deviceis made of two parts: the upper part contains the piston made of metal and a heating device to raise the temperature of the piston up to 500 °C. The lower part is composed of a lead crucible and a glass sample. The assembly is provided with a heating system, an induction furnace of 6 kW for heating the glass up to 950 °C.The developed experimental procedure has permitted in a previous published study to estimate the Thermal Contact ResistanceTCR using the inverse technique developed by Beck [1]. The semi-transparent character of the glass has been taken into account by an additional radiative heat flux and an equivalent thermal conductivity. After the set-up tests, reproducibility experiments for a specific contact pressure have been carried outwith a maximum dispersion that doesn't exceed 6%. Then, experiments under different conditions for a specific glass forming process regarding the application (Packaging, Buildings and Automobile) were carried out. The objective is to determine, experimentallyfor each application,the typical conditions capable to minimize the glass temperature loss during the glass forming process.

  3. Glass transition in binary eutectic systems: best glass-forming composition.

    Science.gov (United States)

    Wang, Li-Min; Li, Zijing; Chen, Zeming; Zhao, Yue; Liu, Riping; Tian, Yongjun

    2010-09-23

    The glass transition and glass-forming ability in a binary eutectic system of methyl o-toluate (MOT) versus methyl p-toluate (MPT) are studied across the whole composition range. The phase diagram is constructed to explore the best glass-forming composition as the characteristic temperatures of the glass transition, crystallization, eutectic, and liquidus are determined. The best vitrification region is found to locate between the eutectic and the midpoint compositions of the eutectic line, indicating a remarkable deviation from the eutectic composition. The compilation of various simple binary eutectic systems covering inorganic, metallic, ionic, and molecular glass-forming liquids reproduces the rule. Kinetics and thermodynamics in binary systems are investigated to associate with the rule. The composition dependence of the structural relaxation time and the kinetic fragility are presented with dielectric measurements. It is found that whereas mixing of binary miscible liquids kinetically favors glass formation, thermodynamic contribution to the deviation of the best glass-forming composition from eutectics is implied.

  4. Zirconium fluoride glass - Surface crystals formed by reaction with water

    Science.gov (United States)

    Doremus, R. H.; Bansal, N. P.; Bradner, T.; Murphy, D.

    1984-01-01

    The hydrated surfaces of a zirconium barium fluoride glass, which has potential for application in optical fibers and other optical elements, were observed by scanning electron microscopy. Crystalline zirconium fluoride was identified by analysis of X-ray diffraction patterns of the surface crystals and found to be the main constituent of the surface material. It was also found that hydrated zirconium fluorides form only in highly acidic fluoride solutions. It is possible that the zirconium fluoride crystals form directly on the glass surface as a result of its depletion of other ions. The solubility of zirconium fluoride is suggested to be probably much lower than that of barium fluoride (0.16 g/100 cu cm at 18 C). Dissolution was determined to be the predominant process in the initial stages of the reaction of the glass with water. Penetration of water into the glass has little effect.

  5. Glass-Forming Ability of Soda Lime Borate Liquids

    DEFF Research Database (Denmark)

    Zheng, Qiuju; Mauro, J.C.; Smedskjær, Morten Mattrup

    2012-01-01

    We investigate the composition dependence of glass-forming ability (GFA) of a series of iron-containing soda lime borate liquids by substituting Na2O for B2O3. We have characterized GFA by measuring the glass stability against crystallization using a differential scanning calorimeter (DSC......). The results show that the GFA decreases when substituting Na2O for B2O3. Moreover, we find that there is no direct link between the kinetic fragility and GFA for the soda lime borate series studied herein. We have also discovered and clarified a striking thermal history dependence of the glass stability...

  6. The glass-forming ability of model metal-metalloid alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai; Liu, Yanhui; Schroers, Jan [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Shattuck, Mark D. [Department of Physics and Benjamin Levich Institute, The City College of the City University of New York, New York, New York 10031 (United States); Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); O’Hern, Corey S. [Department of Mechanical Engineering and Materials Science, Yale University, New Haven, Connecticut 06520 (United States); Center for Research on Interface Structures and Phenomena, Yale University, New Haven, Connecticut 06520 (United States); Department of Physics, Yale University, New Haven, Connecticut 06520 (United States); Department of Applied Physics, Yale University, New Haven, Connecticut 06520 (United States)

    2015-03-14

    Bulk metallic glasses (BMGs) are amorphous alloys with desirable mechanical properties and processing capabilities. To date, the design of new BMGs has largely employed empirical rules and trial-and-error experimental approaches. Ab initio computational methods are currently prohibitively slow to be practically used in searching the vast space of possible atomic combinations for bulk glass formers. Here, we perform molecular dynamics simulations of a coarse-grained, anisotropic potential, which mimics interatomic covalent bonding, to measure the critical cooling rates for metal-metalloid alloys as a function of the atomic size ratio σ{sub S}/σ{sub L} and number fraction x{sub S} of the metalloid species. We show that the regime in the space of σ{sub S}/σ{sub L} and x{sub S} where well-mixed, optimal glass formers occur for patchy and LJ particle mixtures, coincides with that for experimentally observed metal-metalloid glass formers. Thus, our simple computational model provides the capability to perform combinatorial searches to identify novel glass-forming alloys.

  7. The glass-forming ability of model metal-metalloid alloys

    Science.gov (United States)

    Zhang, Kai; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2015-03-01

    Bulk metallic glasses (BMGs) are amorphous alloys with desirable mechanical properties and processing capabilities. To date, the design of new BMGs has largely employed empirical rules and trial-and-error experimental approaches. Ab initio computational methods are currently prohibitively slow to be practically used in searching the vast space of possible atomic combinations for bulk glass formers. Here, we perform molecular dynamics simulations of a coarse-grained, anisotropic potential, which mimics interatomic covalent bonding, to measure the critical cooling rates for metal-metalloid alloys as a function of the atomic size ratio σS/σL and number fraction xS of the metalloid species. We show that the regime in the space of σS/σL and xS where well-mixed, optimal glass formers occur for patchy and LJ particle mixtures, coincides with that for experimentally observed metal-metalloid glass formers. Thus, our simple computational model provides the capability to perform combinatorial searches to identify novel glass-forming alloys.

  8. Microscopic insight into the origin of enhanced glass-forming ability of metallic melts on micro-alloying

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C. J.; Chathoth, S. M., E-mail: smavilac@cityu.edu.hk [Department of Physics and Materials Science, City University of Hong Kong, Kowloon Tong, Hong Kong (China); Podlesnyak, A. [Quantum Condensed Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Mamontov, E. [Chemical and Engineering Materials Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (United States); Wang, W. H. [Institute of Physics, Chinese Academy of Science, Beijing 100190 (China)

    2015-09-28

    Extensive efforts have been made to develop metallic-glasses with large casting diameter. Such efforts were hindered by the poor understanding of glass formation mechanisms and the origin of the glass-forming ability (GFA) in metallic glass-forming systems. In this work, we have investigated relaxation dynamics of a model bulk glass-forming alloy system that shows the enhanced at first and then diminished GFA on increasing the percentage of micro-alloying. The micro-alloying did not have any significant impact on the thermodynamic properties. The GFA increasing on micro-alloying in this system cannot be explained by the present theoretical knowledge. Our results indicate that atomic caging is the primary factor that influences the GFA. The composition dependence of the atomic caging time or residence time is found to be well correlated with GFA of the system.

  9. Exploring Mg-Zn-Ca-Based Bulk Metallic Glasses for Biomedical Applications Based on Thermodynamic Approach

    Science.gov (United States)

    Ramya, M.; Sarwat, Syed Ghazi; Udhayabanu, V.; Raj, Baldev; Ravi, K. R.

    2015-12-01

    Magnesium (Mg)-based metallic glasses are considered as possible candidates in orthopedic implant applications. This paper aims to theoretically predict the glass-forming ability (GFA) in Mg-Zn-Ca alloy using a newly proposed thermodynamic model ( P HHS), and the consistency of this model is verified through experimental analysis. P HHS is based on thermodynamic parameters such as enthalpy of chemical mixing, elastic enthalpy, and configurational entropy, thus incorporating the pivotal effects, i.e., electron transfer effects, effect of atomic size mismatch, and effect of randomness, which aid to high GFA. In essence, P HHS can be visualized as the energy barrier that exists between the transformations of random atomic structure of glass to ordered crystalline structure. When the P HHS value is more negative, the energy barrier will be high, supporting easy glass formation. Various Mg-Zn-Ca metallic glass compositions displayed almost an expected and supporting trend, where the critical diameter of the metallic glass rod increased with a more negative P HHS value. Among the predicted Mg-Zn-Ca systems, the Mg60Zn35Ca5 composition shows deviation from the expected trend. This discrepancy has been clearly elucidated using a eutectic phase diagram. In addition to the consistency of the P HHS parameter to verifying the GFA of various compositions, the unique ability of this model is to predict unexplored Mg-Zn-Ca glass-forming compositions using contour development. Thus, proving P HHS parameter to be used as an efficient tool in predicting new glass-forming compositions.

  10. GSD-1G and MPI-DING Reference Glasses for In Situ and Bulk Isotopic Determination

    Science.gov (United States)

    Jochum, K.P.; Wilson, S.A.; Abouchami, W.; Amini, M.; Chmeleff, J.; Eisenhauer, A.; Hegner, E.; Iaccheri, L.M.; Kieffer, B.; Krause, J.; McDonough, W.F.; Mertz-Kraus, R.; Raczek, I.; Rudnick, R.L.; Scholz, Donna K.; Steinhoefel, G.; Stoll, B.; Stracke, A.; Tonarini, S.; Weis, D.; Weis, U.; Woodhead, J.D.

    2011-01-01

    This paper contains the results of an extensive isotopic study of United States Geological Survey GSD-1G and MPI-DING reference glasses. Thirteen different laboratories were involved using high-precision bulk (TIMS, MC-ICP-MS) and microanalytical (LA-MC-ICP-MS, LA-ICP-MS) techniques. Detailed studies were performed to demonstrate the large-scale and small-scale homogeneity of the reference glasses. Together with previously published isotopic data from ten other laboratories, preliminary reference and information values as well as their uncertainties at the 95% confidence level were determined for H, O, Li, B, Si, Ca, Sr, Nd, Hf, Pb, Th and U isotopes using the recommendations of the International Association of Geoanalysts for certification of reference materials. Our results indicate that GSD-1G and the MPI-DING glasses are suitable reference materials for microanalytical and bulk analytical purposes. Ce document contient les r??sultats d'une importante ??tude isotopique des verres de r??f??rence USGS GSD-1G et MPI-DING. Treize laboratoires diff??rents ont particip?? au travers de techniques analytiques de haute pr??cision travaillant soit sur ??chantillon total (TIMS, MC-ICP-MS) soit par microanalyse ??in situ?? (LA-MC-ICP-MS, LA-ICP-MS). ?? 2010 The Authors. Geostandards and Geoanalytical Research ?? 2010 International Association of Geoanalysts.

  11. Elastic properties of superconducting bulk metallic glasses; Elastische Eigenschaften von supraleitenden massiven metallischen Glaesern

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Marius

    2015-07-01

    Within the framework of this thesis the elastic properties of a superconducting bulk metallic glass between 10 mK and 300 K were first investigated. In order to measure the entire temperature range, in particular the low temperature part, new experimental techniques were developed. Using an inductive readout scheme for a double paddle oscillator it was possible to determine the internal friction and the relative change of sound velocity of bulk metallic glasses with high precision. This allowed for a detailed comparison of the data with different models. The analysis focuses on the low temperature regime where the properties of glassy materials are governed by atomic tunneling systems as described by the tunneling model. The influence of conduction electrons in the normal conducting state and quasiparticles in the superconducting state of the glass were accounted for in the theoretical description, resulting in a good agreement over a large temperature range between measured data and prediction of the tunneling model. This allowed for a direct determination of the coupling constant between electrons and tunneling systems. In the vicinity of the transition temperature Tc the data can only be described if a modified distribution function of the tunneling parameters is applied.

  12. New Ti-based Ti–Cu–Zr–Fe–Sn–Si–Ag bulk metallic glass for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Pang, Shujie; Liu, Ying; Li, Haifei; Sun, Lulu [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li, Yan [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Beijing Key Laboratory for Advanced Functional Materials and Thin Film Technology, Beihang University, Beijing 100191 (China); Zhang, Tao, E-mail: zhangtao@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2015-03-15

    Highlights: • Novel Ti{sub 47}Cu{sub 38}Zr{sub 7.5}Fe{sub 2.5}Sn{sub 2}Si{sub 1}Ag{sub 2} (at.%) bulk metallic glass (BMG) with a critical diameter of 7 mm was discovered. • The present BMG is the largest Ni- and Be-free Ti-based BMG containing low content of noble metal reported to date. • The glassy alloy possesses high specific strength, low Young’s modulus, and good corrosion resistance and bio-compatibility. • Combination of high glass-forming ability and good mechano- and bio-compatibility for the Ti-based BMG demonstrates the potential for use in biomedical applications. - Abstract: A novel Ni-free Ti{sub 47}Cu{sub 38}Zr{sub 7.5}Fe{sub 2.5}Sn{sub 2}Si{sub 1}Ag{sub 2} (at.%) bulk metallic glass (BMG) with superior glass-forming ability, good mechanical properties and excellent biocompatibility was discovered. The Ti-based BMG with a diameter of 7 mm can be prepared by copper mold casting and the supercooled liquid region was 52 K. Compressive strength, specific strength, Young’s modulus and microhardness of the Ti-based BMG were about 2.08 GPa, 3.2 × 10{sup 5} N m/kg, 100 GPa and 588 Hv, respectively. Electrochemical measurements indicated that the Ti-based glassy alloy possesses higher corrosion resistance than Ti–6Al–4V alloy in a simulated body fluid environment. Attachment, spreading out and proliferation of MC3T3-E1 cells on the Ti-based BMG surface demonstrated the excellent biocompatibility. Mechanisms of the formation and properties for the Ti-based glassy alloy are also discussed. The combination of high glass-forming ability, excellent mechanical properties, high corrosion resistance and good biocompatibility demonstrates the potential of the Ni-free Ti-based BMG for use in biomedical applications.

  13. Interpretation of viscous deformation of Zr-based bulk metallic glass alloys based on Nabarro-Herring creep model

    Science.gov (United States)

    Na, Young-Sang; Lee, Jong-Hoon

    2006-04-01

    Superplastic-like viscous deformation of bulk metallic glass alloys around the glass transition temperature (Tg) was analyzed based on the Nabarro-Herring creep model, a classical creep model, where the diffusional motion of atoms or vacancies through the lattice (atomic configuration) is considered. The amorphous matrix of bulk metallic glasses that has a randomly-packed atomic configuration was assumed to behave in a manner similar to the grain boundary in polycrystalline metals so as to approximate the diffusivity of the major constituent element. In spite of rough approximation of the parameters in the Nabarro-Herring creep equation, a reasonable value of the diffusion path (d) could be obtained from the experimentally-obtained metal flow data, including the steady state stress and the strain rate. Due to the absence of vacancy sources such as grain boundaries in homogeneous metallic glasses, the diffusion path, which, in polycrystalline materials, generally is the average distance between vacancy sources such as grain boundaries, was considered in this work as the average distance between tunneling centers in bulk metallic glass alloys. The calculated diffusion path was comparable to the density of tunneling centers around Tg, proposed by M. H. Cohen and G. S. Grest based on free volume theory. The calculated diffusion path showed monotonous decrease with temperature over Tg for Zr-based bulk metallic glass alloys. Based on this analysis, a schematic model for viscous deformation of bulk metallic glass was proposed.

  14. Magnetic properties and microstructural homogeneity in NdFeAl bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ortega-Zempoalteca, R.; Valenzuela, R.; Betancourt, I. [Depto de Materiales Metalicos y Ceramicos, Instituto de Investigaciones en Materiales, UNAM, Avenida Universidad (Mexico)

    2011-11-15

    Bulk metallic glasses of nominal composition Nd{sub 60}Fe{sub 30}Al{sub 10} were prepared by copper mold casting in the form of rods of 3 mm in diameter and 50 mm in length. Preparation conditions were varied to assess the effects of the injection distance and the injection pressure of the melt. In order to determine their microstructure, disk-shaped samples were obtained from different cut zones along the axis rod. A non-homogeneous phase distribution was observed, which resulted from the heat transfer regime during the cooling of the melt in the copper mold. As expected, the nature, distribution and volumetric fraction of the various phases produced play an important role on the resulting magnetic properties. Among the main observed phases are Fe-rich rod-like crystals, Nd-rich dendritic crystals and a ''like-amorphous'' matrix. The hard magnetic properties of these materials can be associated with this matrix. In these cooling regimes, the coercive field increases as the cooling rate of the amorphous matrix increases. Hysteresis loops showed a high degree of coupling between phases with different magnetic order. Both the coercive field and the magnetization showed a significant variation along the rod axis; a maximum appeared as a function of the axis length. In order to gather more information about the coupling between the observed phases, {delta}M (or Henkel) plots were obtained, showing an exchange character for interactions (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  15. Light Emission and Dynamic Failure Mechanism of Hypervelocity Impact on Zr-Ti-Ni-Cu-Be Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    SUN Bao-Ru; ZHAN Zai-Ji; LIANG Bo; ZHANG Rui-Jun; WANG Wen-Kui

    2011-01-01

    Hypervelocity impact on rectangular plate-shaped ZrnThtCuw.sNiioB^.s bulk metallic glass (BMG) is performed by a two-stage light gas gun. The targets used in the experiment are BMG plates with a thickness of 5 mm. The projectile, spherical aluminum (3.1 mm in diameter), is accelerated up to various velocities; the light is detected with a radiometer. The emission lasts from 200 \\is up to 1500 \\is and the intensity increases from 44 to 900 W/(Sr-\\im). The duration and intensity of a light emission seem to depend on the impact velocity and the extent of target destruction through the formation of impact craters or penetration.%@@ Hypervelocity impact on rectangular plate-shaped Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass(BMG)is per-formed by a two-stage light gas gun.The targets used in the experiment are BMG plates with a thickness of 5 mm.The projectile,spherical aluminum(3.1 mm in diameter),is accelerated up to various velocities;the light is detected with a radiometer.The emission lasts from 200μs up to 1500μs and the intensity increases from 44 extent of target destruction through the formation of impact craters or penetration.

  16. Crystallization in Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass under pressure

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Zhou, T.J.; Rasmussen, Helge Kildahl

    2000-01-01

    The effect of pressure on the crystallization behavior of the bulk metallic glass-forming Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy with a wide supercooled liquid region has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction measurements using synchrotron radiation......)], reporting a decrease of the crystallization temperature under pressure in a pressure range of 0-6 GPa for the bulk glass Zr41Ti14Cu12.5Ni9Be22.5C1 alloy. Compressibility with a volume reduction of approximately 22% at room temperature does not induce crystallization in the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk...... glass alloy. This indicates that the densification effect induced by pressure in the pressure range investigated plays a minor role in the crystallization behavior of this bulk glass alloy. The different crystallization behavior of the carbon-free and the carbon-containing glassy alloys has been...

  17. Femtosecond laser writing of Bragg grating waveguide bundles in bulk glass.

    Science.gov (United States)

    Thiel, Markus; Flachenecker, Günter; Schade, Wolfgang

    2015-04-01

    Waveguide bundles in bulk glass materials, consisting of several parallel scans of refractive index modifications, have been generated with a low-repetition femtosecond laser. Additionally, Bragg grating (BG) structures for 840 and 1550 nm have been introduced by segmentation of the central scan. A spectral loss in the transmission signal of >36  dB was achieved at 1550 nm with a second-order Bragg grating waveguide (BGW) in fused silica, which corresponds to an intrinsic grating efficiency of >16  dB/cm. This is to our knowledge the strongest BG structure realized in glass with a femtosecond laser. The BGW were proven to be stable up to a temperature of 250°C in fused silica. The diameter of the waveguide bundles can be adapted very easily for a broad range of wavelengths and have been demonstrated for diameters between 1 and 50 μm. The transmission properties of the waveguide bundles are affected minorly by the insertion of BG structures, which opens the ability for adjusting the BGW for a broad range of wavelength in single-mode or multimode optical circuits. BGW have been realized successfully in fused silica, borosilicate glass (BOROFLOAT 33), and AF 32 eco Thin Glass from Schott.

  18. Improved plasticity by electropulsing in a Zr62Al19Ni19 bulk metallic glass

    Science.gov (United States)

    Zhang, J. L.; Lu, J. X.; Shek, C. H.

    2009-01-01

    The present work reported the application of electropulsing technique (EPT) for improving plasticity of a Zr62Al19Ni19 bulk metallic glass. After the elecropulsing with a small current of 5A, no obvious crystallization was observed in X-ray diffraction (XRD) patterns. Results of differential scanning calorimetry (DSC) measurements indicated that the glass transition temperature was reduced from 698K to 691K. Room-temperature uniaxial compression tests revealed that the treated BMG showed larger plastic deformation up to 6%, compared with less than 2% plasticity of untreated sample, at a 1×10-4 s-1 strain rate. SEM observation showed that the sample after electropulsing treatment show significant difference in the distribution of shear bands from that of the untreated one.

  19. Elastic properties of Pd40Cu30Ni10P20 bulk glass in supercooled liquid region

    DEFF Research Database (Denmark)

    Nishiyama, N.; Inoue, A.; Jiang, Jianzhong

    2001-01-01

    In situ ultrasonic measurements for the Pd40Cu30Ni10P20 bulk glass in three states: Glassy solid, supercooled liquid, and crystalline, have been performed. It is found that velocities of both longitudinal and transverse waves and elastic moduli (shear modulus, bulk modulus, Young's modulus, and L...

  20. Short-to-Medium-Range Order and Atomic Packing in Zr48Cu36Ag8Al8 Bulk Metallic Glass

    Directory of Open Access Journals (Sweden)

    Yong Xu

    2016-10-01

    Full Text Available Due to its excellent glass-forming ability (GFA, the Zr48Cu36Al8Ag8 bulk metallic glass (BMG is of great importance in glass transition investigations and new materials development. However, due to the lack of detailed structural information, the local structure and atomic packing of this alloy is still unknown. In this work, synchrotron measurement and reverse Monte Carlo simulation are performed on the atomic configuration of a Zr-based bulk metallic glass. The local structure is characterized in terms of bond pairs and Voronoi tessellation. It is found that there are mainly two types of bond pairs in the configuration, as the body-centered cubic (bcc-type and icosahedral (ico-type bond pairs. On the other hand, the main polyhedra in the configuration are icosahedra and the bcc structure. That is, the bcc-type bond pairs, together with the ico-type bond pairs, form the bcc polyhedra, introducing the distortion in bcc clusters in short range. However, in the medium range, the atoms formed linear or planar structures, other than the tridimensional clusters. That is, the medium-range order in glass is of 1D or 2D structure, suggesting the imperfect ordered packing feature.

  1. Non-Magnetic, Tough, Corrosion- and Wear-Resistant Knives From Bulk Metallic Glasses and Composites

    Science.gov (United States)

    Hoffman, Douglas C.; Potter, Benjamin

    2013-01-01

    Quality knives are typically fabricated from high-strength steel alloys. Depending on the application, there are different requirements for mechanical and physical properties that cause problems for steel alloys. For example, diver's knives are generally used in salt water, which causes rust in steel knives. Titanium diver's knives are a popular alternative due to their salt water corrosion resistance, but are too soft to maintain a sharp cutting edge. Steel knives are also magnetic, which is undesirable for military applications where the knives are used as a tactical tool for diffusing magnetic mines. Steel is also significantly denser than titanium (8 g/cu cm vs. 4.5 g/cu cm), which results in heavier knives for the same size. Steel is hard and wear-resistant, compared with titanium, and can keep a sharp edge during service. A major drawback of both steel and titanium knives is that they must be ground or machined into the final knife shape from a billet. Since most knives have a mirrored surface and a complex shape, manufacturing them is complex. It would be more desirable if the knife could be cast into a net or near-net shape in a single step. The solution to the deficiencies of titanium, steel, and ceramic knives is to fabricate them using bulk metallic glasses (or composites). These alloys can be cast into net or near-net shaped knives with a combination of properties that exceed both titanium and steel. A commercially viable BMG (bulk metallic glass) or composite knife is one that exhibits one or all of the following properties: It is based on titanium, has a self-sharpening edge, can retain an edge during service, is hard, is non-magnetic, is corrosion-resistant against a variety of corrosive environments, is tough (to allow for prying), can be cast into a net-shape with a mirror finish and a complex shape, has excellent wear resistance, and is low-density. These properties can be achieved in BMG and composites through alloy chemistry and processing. For

  2. Glass-Forming Ability of an Iron-Based Alloy Enhanced by Co Addition and Evaluated by a New Criterion

    Institute of Scientific and Technical Information of China (English)

    CHEN Qing-Jun; SHEN Jun; FAN Hong-Bo; SUN Jian-Fei; HUANG Yong-Jiang; MCCARTNEY D. G.

    2005-01-01

    @@ A new Fe-based alloy that can be cast into a fully amorphous rod with a diameter of at least 16mm by the conventional copper-mould casting technique is obtained by partially replacing Fe with Co in a previously reported Fe-based bulk metallic glass. The preliminary thermodynamic analysis indicates that the Co-containing alloy has a significantly lower Gibbs free energy difference between the undercooled melt and the corresponding crystalline solid, compared to the Co-free alloy, reflecting the dramatic role of the Co addition in stabilizing the supercooled melt and facilitating glass formation in iron-based alloys. Here, a new criterion, derived from the classical nucleation and growth theory, is introduced to evaluate the glass-forming ability of Fe-based bulk metallic glasses.

  3. Excellent Magnetocaloric Effect in Er6oAl18Co22 Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    HUI Xi-Dong; XU Zhi-Yi; WANG En-Rui; CHEN Guo-Liang; LU Zhao-Ping

    2010-01-01

    @@ Excellent magnetocaloric effect with a maximum entropy change and refrigeration capacity of 17.6 J.kg-1.K-1 and 546 J.kg-1,respectively,has been discovered in the Er60Al18 Co22 bulk metallic glass under the fleld of 50 kOe in the temperature range of helium liquefaction.This MCE results from the second-order magnetic transition from the paramagnetic to the ferromagnetic state.Our analysis based on mean-field theory suggests that the excellent MCE is attributed to the strong exchange of magnetic moment in the glassy structure.

  4. Nearest-neighbor coordination and chemical ordering in multi-component bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Dong [ORNL; Stoica, Alexandru Dan [ORNL; Yang, Ling [ORNL; Wang, Xun-Li [ORNL; Lu, Zhao Ping [ORNL; Neuefeind, Joerg C [ORNL; Kramer, Matthew J [ORNL; Richardson, James W [Argonne National Laboratory (ANL); Proffen, Thomas E [ORNL

    2007-01-01

    We report complimentary use of high energy x-ray and neutron diffraction to probe the local atomic structure in a Zr-based multi-component bulk metallic glass. By analyzing the partial coordination numbers, we demonstrate the presence of multiple types of solute-centered clusters (or the lack of solute-solute bonding) and efficient packing of the amorphous structure at the atomic scale. Our findings provide a basis for understanding how the local structures change during phase transformation and mechanical deformation.

  5. Fatigue Properties and Morphology of Fatigue Fracture of Bulk Metallic Glass

    Science.gov (United States)

    Zhao, X. Y.; Chen, Z. H.; Wang, H. P.; Zhan, J.

    2016-11-01

    Changes in the amorphous structure and fatigue resistance of Zr57.5Cu27.3Al8.5Ni6.7 bulk metallic glass are studied. A copper-rich phase produced by cyclic stresses is discovered. This phase observed on the fracture surface may hinder crack propagation. The specimens after fatigue failure have a V shape (do not break into two completely) due to the high density of shear bands and multiple branching of the shear bands in the strained region.

  6. Crystallization mechanism of CeAlFeCo bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    王志新; 卢金斌; 席艳君

    2010-01-01

    Crystallization behaviors of Ce60Al15Fe5+xCo20-x(x=0,5,10) bulk metallic glasses(BMGs) were studied by means of differential scanning calorimeter(DSC) and X-ray diffraction(XRD).The crystallization processes of different samples were simulated by JMA equation.Experimental results demonstrated that incubation and crystallization time increased with decreasing isothermal temperature for the same sample.The crystallization mechanism of CeAlFeCo BMGs was discussed.

  7. Crystallization and thermophysical properties of Cu46Zr47Al6Co1 bulk metallic glass

    Directory of Open Access Journals (Sweden)

    Kang Wu

    2013-11-01

    Full Text Available Phase evolution of two-step crystallization and the subsequent B2-phase transformation was presented in Cu46Zr47Al6Co1 bulk metallic glass (BMG during heating process. Thermophysical properties, i.e. the thermal diffusivity and the specific heat capacity, of the BMG in amorphous solid state and supercooled liquid state as well as its crystalline counterparts were measured from room temperature to 1070 K. The thermal conductivity was also calculated through combination of the data of the thermal diffusivity and the specific heat capacity. The possible influence of the crystallization on the thermophysical properties was discussed.

  8. Modeling deformation behavior of Cu-Zr-Al bulk metallic glass matrix composites

    Science.gov (United States)

    Pauly, S.; Liu, G.; Wang, G.; Das, J.; Kim, K. B.; Kühn, U.; Kim, D. H.; Eckert, J.

    2009-09-01

    In the present work we prepared an in situ Cu47.5Zr47.5Al5 bulk metallic glass matrix composite derived from the shape memory alloy CuZr. We use a strength model, which considers percolation and a three-microstructural-element body approach, to understand the effect of the crystalline phase on the yield stress and the fracture strain under compressive loading, respectively. The intrinsic work-hardenability due to the martensitic transformation of the crystalline phase causes significant work hardening also of the composite material.

  9. Deformation-induced martensitic transformation in Cu-Zr-Al(Ti) bulk metallic glass composites

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Ram Bachchan; Pauly, Simon; Das, Jayanta; Eckert, Juergen [Institut fuer Komplexe Materialien, IFW Dresden (Germany)

    2009-07-01

    Plastic deformation of Cu-Zr-(Al, Ti) bulk metallic glass (BMG) composites induces a martensitic phase transformation from the B2 to the B19* CuZr phase. Addition of Ti to binary Cu-Zr increases the temperature above which the B2 CuZr phase becomes stable. This affects the phase formation upon quenching in Cu-Zr-Ti BMG composites. The deformation-induced martensitic transformation is believed to cause the strong work hardening and to contribute to the large compressive deformability with plastic strains up to 15%.

  10. Castable Bulk Metallic Glass Strain Wave Gears: Towards Decreasing the Cost of High-Performance Robotics

    Science.gov (United States)

    Hofmann, Douglas C.; Polit-Casillas, Raul; Roberts, Scott N.; Borgonia, John-Paul; Dillon, Robert P.; Hilgemann, Evan; Kolodziejska, Joanna; Montemayor, Lauren; Suh, Jong-Ook; Hoff, Andrew; Carpenter, Kalind; Parness, Aaron; Johnson, William L.; Kennett, Andrew; Wilcox, Brian

    2016-11-01

    The use of bulk metallic glasses (BMGs) as the flexspline in strain wave gears (SWGs), also known as harmonic drives, is presented. SWGs are unique, ultra-precision gearboxes that function through the elastic flexing of a thin-walled cup, called a flexspline. The current research demonstrates that BMGs can be cast at extremely low cost relative to machining and can be implemented into SWGs as an alternative to steel. This approach may significantly reduce the cost of SWGs, enabling lower-cost robotics. The attractive properties of BMGs, such as hardness, elastic limit and yield strength, may also be suitable for extreme environment applications in spacecraft.

  11. Broadband directional couplers fabricated in bulk glass with high repetition rate femtosecond laser pulses.

    Science.gov (United States)

    Chen, Wei-Jen; Eaton, Shane M; Zhang, Haibin; Herman, Peter R

    2008-07-21

    A femtosecond fiber laser was applied to fabricate broadband directional couplers inside bulk glass for general power splitting application in the 1250 to 1650-nm wavelength telecom spectrum. The broadband response was optimized over the 400-nm bandwidth by tailoring the coupling strength and the waveguide interaction length to balance the differing wavelength dependence of the straight interaction and bent transition regions. High spatial finesse of the femtosecond-laser writing technique enabled close placement (approxiamtely 6 microm) of adjacent waveguides that underpinned the wavelength-flattened broadband response at any coupling ratio in the 0% to 100% range. The spectral responses were well-represented by coupled mode theory, permitting simple design and implementation of broadband couplers for bulk 3D optical circuit integration.

  12. Pronounced Plasticity Caused by Phase Separation and β-relaxation Synergistically in Zr-Cu-Al-Mo Bulk Metallic Glasses.

    Science.gov (United States)

    Wang, Tuo; Wang, Lu; Wang, Qinjia; Liu, Yanhui; Hui, Xidong

    2017-04-27

    Bulk metallic glasses (BMGs) are known to have extraordinary merits such as ultrahigh strength and dynamic toughness etc. but tied to the detrimental brittleness, which has become a critical issue to the engineering application and understanding the glass nature. In this article, we report a new class of Zr-Cu-Al-Mo BMGs with extraordinary plastic strain above 20%. "Work-hardening" effect after yielding in a wide range of plastic deformation process has been detected for this kind of BMGs. Compositional heterogeneity, which can be classified into ZrMo- and Cu-rich zones, was differentiated in this kind of BMG. Pronounced humps have been observed on the high frequency kinetic spectrum in Mo containing BMGs, which is the indicator of β-relaxation transition. The underlying mechanism for the excellent plastic deforming ability of this class of BMGs is ascribed to the synergistic effects of soft ZrMo-rich glass formed through phase separation and abundant flow units which related to β-relaxation.

  13. Asymmetric crystallization during cooling and heating in model glass-forming systems.

    Science.gov (United States)

    Wang, Minglei; Zhang, Kai; Li, Zhusong; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D; O'Hern, Corey S

    2015-03-01

    We perform molecular dynamics (MD) simulations of the crystallization process in binary Lennard-Jones systems during heating and cooling to investigate atomic-scale crystallization kinetics in glass-forming materials. For the cooling protocol, we prepared equilibrated liquids above the liquidus temperature Tl and cooled each sample to zero temperature at rate Rc. For the heating protocol, we first cooled equilibrated liquids to zero temperature at rate Rp and then heated the samples to temperature T>Tl at rate Rh. We measured the critical heating and cooling rates Rh* and Rc*, below which the systems begin to form a substantial fraction of crystalline clusters during the heating and cooling protocols. We show that Rh*>Rc* and that the asymmetry ratio Rh*/Rc* includes an intrinsic contribution that increases with the glass-forming ability (GFA) of the system and a preparation-rate dependent contribution that increases strongly as Rp→Rc* from above. We also show that the predictions from classical nucleation theory (CNT) can qualitatively describe the dependence of the asymmetry ratio on the GFA and preparation rate Rp from the MD simulations and results for the asymmetry ratio measured in Zr- and Au-based bulk metallic glasses (BMG). This work emphasizes the need for and benefits of an improved understanding of crystallization processes in BMGs and other glass-forming systems.

  14. On the origin of multi-component bulk metallic glasses: Atomic size mismatches and de-mixing

    Science.gov (United States)

    Zhang, Kai; Dice, Bradley; Liu, Yanhui; Schroers, Jan; Shattuck, Mark D.; O'Hern, Corey S.

    2015-08-01

    The likelihood that an undercooled liquid vitrifies or crystallizes depends on the cooling rate R . The critical cooling rate R c , below which the liquid crystallizes upon cooling, characterizes the glass-forming ability (GFA) of the system. While pure metals are typically poor glass formers with R c > 1 0 12 K/s , specific multi-component alloys can form bulk metallic glasses (BMGs) even at cooling rates below R ˜ 1 K / s . Conventional wisdom asserts that metal alloys with three or more components are better glass formers (with smaller R c ) than binary alloys. However, there is currently no theoretical framework that provides quantitative predictions for R c for multi-component alloys. In this manuscript, we perform simulations of ternary hard-sphere systems, which have been shown to be accurate models for the glass-forming ability of BMGs, to understand the roles of geometric frustration and demixing in determining R c . Specifically, we compress ternary hard sphere mixtures into jammed packings and measure the critical compression rate, below which the system crystallizes, as a function of the diameter ratios σB/σA and σC/σA and number fractions xA, xB, and xC. We find two distinct regimes for the GFA in parameter space for ternary hard spheres. When the diameter ratios are close to 1, such that the largest (A) and smallest (C) species are well-mixed, the GFA of ternary systems is no better than that of the optimal binary glass former. However, when σC/σA ≲ 0.8 is below the demixing threshold for binary systems, adding a third component B with σC < σB < σA increases the GFA of the system by preventing demixing of A and C. Analysis of the available data from experimental studies indicates that most ternary BMGs are below the binary demixing threshold with σC/σA < 0.8.

  15. Super-Potts glass: A disordered model for glass-forming liquids

    Science.gov (United States)

    Angelini, Maria Chiara; Biroli, Giulio

    2014-12-01

    We introduce a disordered system, the super-Potts model, which is a more frustrated version of the Potts glass. Its elementary degrees of freedom are variables that can take M values and are coupled via pairwise interactions. Its exact solution on a completely connected lattice demonstrates that, for large enough M , it belongs to the class of mean-field systems solved by a one-step replica symmetry breaking ansatz. Numerical simulations by the parallel tempering technique show that in three dimensions it displays a phenomenological behavior similar to the one of glass-forming liquids. The super-Potts glass is therefore a disordered model allowing one to perform extensive and detailed studies of the random first-order transition in finite dimensions. We also discuss its behavior for small values of M , which is similar to the one of spin glasses in a field.

  16. Transparent form-active system with structural glass

    NARCIS (Netherlands)

    Nikolaou, M.S.N.; Veer, F.A.; Eigenraam, P.

    2015-01-01

    Free-form transparent wide-span spatial structures which have being constructed so far, are based on the concept of three sets of components, the structural components, usually steel elements to ensure both compressive and tensional capacity; the glass cladding elements for expressing transparency;

  17. Transparent form-active system with structural glass

    NARCIS (Netherlands)

    Nikolaou, M.S.N.; Veer, F.A.; Eigenraam, P.

    2015-01-01

    Free-form transparent wide-span spatial structures which have being constructed so far, are based on the concept of three sets of components, the structural components, usually steel elements to ensure both compressive and tensional capacity; the glass cladding elements for expressing transparency;

  18. Microstructure and mechanical properties of Zr-Cu-Al bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Zr49Cu46Al5 and Zr48.5Cu46.5Al5 bulk metallic glasses(BMGs) with diameter of 5 mm were prepared through water-cooled copper mold casting. The phase structures of the two alloys were identified by X-ray diffractometry(XRD). The thermal stability was examined by differential scanning calorimetry(DSC). Zr49Cu46Al5 alloy shows a glass transition temperature, Tg, of about 689 K, an crystallization temperature, Tx, of about 736 K. The Zr48.5Cu46.5Al5 alloy shows no obvious exothermic peak. The microstructure of the as-cast alloys was analyzed by transmission electron microscopy(TEM). The aggregations of CuZr and CuZr2 nanocrystals with grain size of about 20 nm are observed in Zr49Cu46Al5 nanocrystalline composite, while the Zr48.5Cu46.5Al5 alloy containing many CuZr rmartensite plates is crystallized seriously. Mechanical properties of bulk Zr49Cu46Al5 nanocrystalline composite and Zr48.5Cu46.5Al5 alloy measured by compression tests at room temperature show that the work hardening ability of Zr48.5Cu46.5Al5 alloy is larger than that of Zr49Cu46Al5 alloy.

  19. Hot Embossing of Zr-Based Bulk Metallic Glass Micropart Using Stacked Silicon Dies

    Directory of Open Access Journals (Sweden)

    Zhijing Zhu

    2015-01-01

    Full Text Available We demonstrated hot embossing of Zr65Cu17.5Ni10Al7.5 bulk metallic glass micropart using stacked silicon dies. Finite element simulation was carried out, suggesting that it could reduce the stress below 400 MPa in the silicon dies and enhance the durability of the brittle silicon dies when using varying load mode (100 N for 60 s and then 400 N for 60 s compared with using constant load mode (200 N for 120 s. A micropart with good appearance was fabricated under the varying load, and no silicon die failure was observed, in agreement with the simulation. The amorphous state of the micropart was confirmed by differential scanning calorimeter and X-ray diffraction, and the nanohardness and Young’s modulus were validated close to those of the as-cast BMG rods by nanoindentation tests. The results proved that it was feasible to adopt the varying load mode to fabricate three-dimensional Zr-based bulk metallic glass microparts by hot embossing process.

  20. Comparison of mechanical properties of glass-bonded sodalite and borosilicate glass high-level waste forms

    Energy Technology Data Exchange (ETDEWEB)

    O' Holleran, T. P.; DiSanto, T.; Johnson, S. G.; Goff, K. M.

    2000-05-09

    Argonne National Laboratory has developed a glass-bonded sodalite waste form to immobilize the salt waste stream from electrometallurgical treatment of spent nuclear fuel. The waste form consists of 75 vol.% crystalline sodalite and 25 vol.% glass. Microindentation fracture toughness measurements were performed on this material and borosilicate glass from the Defense Waste Processing Facility using a Vickers indenter. Palmqvist cracking was confined for the glass-bonded sodalite waste form, while median-radial cracking occurred in the borosilicate glass. The elastic modulus was measured by an acoustic technique. Fracture toughness, microhardness, and elastic modulus values are reported for both waste forms.

  1. Effect of physical aging on Johari-Goldstein relaxation in La-based bulk metallic glass

    Science.gov (United States)

    Qiao, Jichao; Casalini, Riccardo; Pelletier, Jean-Marc

    2014-09-01

    The influence of physical aging on the β relaxation in La60Ni15Al25 bulk metallic glass has been investigated by mechanical spectroscopy. The amplitude of the β relaxation (ΔG″) decreases while its relaxation time (τβ) increases during aging. We find that, as in organic glasses, the changes of ln (τβ) and ln (ΔGmax ) are linearly correlated with ln (τβ) = b - a ln (G_max^''). This behavior is discussed in term of the asymmetric double-well potential (ADWP) model, with U and Δ the energies characterizing the ADWP. It is suggested that during aging the ratio U/Δ remains approximately constant, with a value close to the coefficient describing the linear correlation between ln (τβ) and ln (G_max^'')(U/Δ ˜ a). Moreover, the evolution versus aging time of ΔGmax can be described by a simple stretched exponential equation giving values of τaging consistent with tan(δ) measurements during aging. The very similar behavior of the β relaxation during aging in metallic glasses and organic material strongly suggests a common nature for this relaxation.

  2. Joining and Assembly of Bulk Metallic Glass Composites Through Capacitive Discharge

    Science.gov (United States)

    Hofmann, Douglas C.; Roberts, Scott; Kozachkov, Henry; Demetriou, Marios D.; Schramm, Joseph P.; Johnson, William L.

    2012-01-01

    Bulk metallic glasses (BMGs), a class of amorphous metals defined as having a thickness greater than 1 mm, are being broadly investigated by NASA for use in spacecraft hardware. Their unique properties, attained from their non-crystalline structure, motivate several game-changing aerospace applications. BMGs have low melting temperatures so they can be cheaply and repeatedly cast into complex net shapes, such as mirrors or electronic casings. They are extremely strong and wear-resistant, which motivates their use in gears and bearings. Amorphous metal coatings are hard, corrosion-resistant, and have high reflectivity. BMG composites, reinforced with soft second phases, can be fabricated into energy-absorbing cellular panels for orbital debris shielding. One limitation of BMG materials is their inability to be welded, bonded, brazed, or fastened in a convenient method to form larger structures. Cellular structures (which can be classified as trusses, foams, honeycombs, egg boxes, etc.) are useful for many NASA, commercial, and military aerospace applications, including low-density paneling and shields. Although conventional cellular structures exhibit high specific strength, their porous structures make them challenging to fabricate. In particular, metal cellular structures are extremely difficult to fabricate due to their high processing temperatures. Aluminum honeycomb sandwich panels, for example, are used widely as spacecraft shields due to their low density and ease of fabrication, but suffer from low strength. A desirable metal cellular structure is one with high strength, combined with low density and simple fabrication. The thermoplastic joining process described here allows for the fabrication of monolithic BMG truss-like structures that are 90% porous and have no heat-affected zone, weld, bond, or braze. This is accomplished by welding the nodes of stacked BMG composite panels using a localized capacitor discharge, forming a single monolithic structure

  3. Dilute condition corrosion behavior of glass-ceramic waste form

    Science.gov (United States)

    Crum, Jarrod V.; Neeway, James J.; Riley, Brian J.; Zhu, Zihua; Olszta, Matthew J.; Tang, Ming

    2016-12-01

    Borosilicate glass-ceramics are being developed to immobilize high-level waste generated by aqueous reprocessing into a stable waste form. The corrosion behavior of this multiphase waste form is expected to be complicated by multiple phases and crystal-glass interfaces. A modified single-pass flow-through test was performed on polished monolithic coupons at a neutral pH (25 °C) and 90 °C for 33 d. The measured glass corrosion rates by micro analysis in the samples ranged from 0.019 to 0.29 g m-2 d-1 at a flow rate per surface area = 1.73 × 10-6 m s-1. The crystal phases (oxyapatite and Ca-rich powellite) corroded below quantifiable rates, by micro analysis. While, Ba-rich powellite corroded considerably in O10 sample. The corrosion rates of C1 and its replicate C20 were elevated an order of magnitude by mechanical stresses at crystal-glass interface caused by thermal expansion mismatch during cooling and unique morphology (oxyapatite clustering).

  4. Roles of nanoclusters in shear banding and plastic deformation of bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Nieh, T G

    2012-07-31

    During the course of this research we published 33 papers in various physics/material journals. We select four representing papers in this report and their results are summarized as follows. I. To study shear banding process, it is pertinent to know the intrinsic shear strain rate within a propagating shear band. To this aim, we used nanoindentation technique to probe the mechanical response of a Au49Ag5.5Pd2.3Cu26.9Si16.3 bulk metallic glass in locality and found notable pop-in events associated with shear band emission. Using a free volume model and under the situation when temperature and stress/hardness are fixed result in an equation, which predicts that hardness serration caused by pop-in decreases exponentially with the strain rate. Our data are in good agreement with the prediction. The result also predicts that, when strain rate is higher than a critical strain rate of 1700 s^-1, there will be no hardness serration, thereby no pop-in. In other words, multiple shear bandings will take place and material will flow homogeneously. The critical strain rate of 1700 s^-1 can be treated as the intrinsic strain rate within a shear band. We subsequently carried out a simulation study and showed that, if the imposed strain rate was over , the shear band spacing would become so small that the entire sample would virtually behave like one major shear band. Using the datum strain rate =1700 s^-1 and based on a shear band nucleation model proposed by us, the size of a shear-band nucleus in Au-BMG was estimated to be 3 10^6 atoms, or a sphere of ~30 nm in diameter. II. Inspired by the peculiar result published in a Science article Super Plastic Bulk Metallic Glasses at Room Temperature, we synthesized the Zr-based bulk metallic glass with a composition identical to that in the paper (Zr64.13Cu15.75Ni10.12Al10) and, subsequently, tested in compression at the same slow strain rate (~10^-4 s^-1). We found that the dominant deformation mode is always single shear. The stress

  5. Low sintering temperature glass waste forms for sequestering radioactive iodine

    Science.gov (United States)

    Nenoff, Tina M.; Krumhansl, James L.; Garino, Terry J.; Ockwig, Nathan W.

    2012-09-11

    Materials and methods of making low-sintering-temperature glass waste forms that sequester radioactive iodine in a strong and durable structure. First, the iodine is captured by an adsorbant, which forms an iodine-loaded material, e.g., AgI, AgI-zeolite, AgI-mordenite, Ag-silica aerogel, ZnI.sub.2, CuI, or Bi.sub.5O.sub.7I. Next, particles of the iodine-loaded material are mixed with powdered frits of low-sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, ranging from 425.degree. C. to 550.degree. C. The sintering converts the mixed powders into a solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500.degree. C. (below the silver iodide sublimation temperature of 500.degree. C.) was identified that contains oxides of boron, bismuth, and zinc, while containing essentially no lead or silicon.

  6. Atomic-Scale Mechanisms of the Glass-Forming Ability in Metallic Glasses

    Science.gov (United States)

    Yang, L.; Guo, G. Q.; Chen, L. Y.; Huang, C. L.; Ge, T.; Chen, D.; Liaw, P. K.; Saksl, K.; Ren, Y.; Zeng, Q. S.; LaQua, B.; Chen, F. G.; Jiang, J. Z.

    2012-09-01

    The issue, composition dependence of glass-forming ability (GFA) in metallic glasses (MG), has been investigated by systematic experimental measurements coupled with theoretical calculations in Cu-Zr and Ni-Nb alloy systems. It is found that the atomic-level packing efficiency strongly relates to their GFA. The best GFA is located at the largest difference in the packing efficiency of the solute-centered clusters between the glassy and crystal alloys in both MG systems. This work provides an understanding of GFA from atomic level and will shed light on the development of new MGs with larger critical sizes.

  7. Onset of Cooperative Dynamics in an Equilibrium Glass-Forming Metallic Liquid.

    Science.gov (United States)

    Jaiswal, Abhishek; O'Keeffe, Stephanie; Mills, Rebecca; Podlesynak, Andrey; Ehlers, Georg; Dmowski, Wojciech; Lokshin, Konstantin; Stevick, Joseph; Egami, Takeshi; Zhang, Yang

    2016-02-18

    Onset of cooperative dynamics has been observed in many molecular liquids, colloids, and granular materials in the metastable regime on approaching their respective glass or jamming transition points, and is considered to play a significant role in the emergence of the slow dynamics. However, the nature of such dynamical cooperativity remains elusive in multicomponent metallic liquids characterized by complex many-body interactions and high mixing entropy. Herein, we report evidence of onset of cooperative dynamics in an equilibrium glass-forming metallic liquid (LM601: Zr51Cu36Ni4Al9). This is revealed by deviation of the mean effective diffusion coefficient from its high-temperature Arrhenius behavior below TA ≈ 1300 K, i.e., a crossover from uncorrelated dynamics above TA to landscape-influenced correlated dynamics below TA. Furthermore, the onset/crossover temperature TA in such a multicomponent bulk metallic glass-forming liquid is observed at approximately twice of its calorimetric glass transition temperature (Tg ≈ 697 K) and in its stable liquid phase, unlike many molecular liquids.

  8. Glass-forming liquids: one or more "order" parameters"

    DEFF Research Database (Denmark)

    Bailey, Nicholas; Christensen, Tage Emil; Jakobsen, Bo

    2008-01-01

    that a description with a single "order" parameter applies to a good approximation whenever thermal equilibrium fluctuations of fundamental variables like energy and pressure are strongly correlated. Results from computer simulations showing that this is the case for a number of simple glass-forming liquids, as well......We first summarize the classical arguments that the vast majority of glass-forming liquids require more than one ‘order' parameter for their description. Critiques against this conventional wisdom are then presented, and it is argued that the matter deserves to be reconsidered in the light...... as a few exceptions, are briefly presented. Finally, we briefly discuss a new conjecture according to which experiments at varying temperature and pressure follow the density scaling expression for the relaxation time, τ = F(ρ^x/T ) (ρ and T are density and temperature), if and only if the liquid...

  9. CHARACTERIZATION OF PLASTICALLY-INDUCED STRUCTURAL CHANGES IN A Zr-BASED BULK METALLIC GLASS USING POSITRON ANNIHILATION SPECTROCOPY

    Energy Technology Data Exchange (ETDEWEB)

    Flores, K M; Kanungo, B P; Glade, S C; Asoka-Kumar, P

    2005-09-16

    Flow in metallic glasses is associated with stress-induced cooperative rearrangements of small groups of atoms involving the surrounding free volume. Understanding the details of these rearrangements therefore requires knowledge of the amount and distribution of the free volume and how that distribution evolves with deformation. The present study employs positron annihilation spectroscopy to investigate the free volume change in Zr{sub 58.5}Cu{sub 15.6}Ni{sub 12.8}Al{sub 10.3}Nb{sub 2.8} bulk metallic glass after inhomogeneous plastic deformation by cold rolling and structural relaxation by annealing. Results indicate that the size distribution of open volume sites is at least bimodal. The size and concentration of the larger group, identified as flow defects, changes with processing. Following initial plastic deformation the size of the flow defects increases, consistent with the free volume theory for flow. Following more extensive deformation, however, the size distribution of the positron traps shifts, with much larger open volume sites forming at the expense of the flow defects. This suggests that a critical strain is required for flow defects to coalesce and form more stable nanovoids, which have been observed elsewhere by high resolution TEM. Although these results suggest the presence of three distinct open volume size groups, further analysis indicates that all groups have the same line shape parameter. This is in contrast to the distinctly different interactions observed in crystalline materials with multiple defect types. This similarity may be due to the disordered structure of the glass and positron affinity to particular atoms surrounding open-volume regions.

  10. Structural disorder in metallic glass-forming liquids

    OpenAIRE

    Shao-Peng Pan; Shi-Dong Feng; Li-Min Wang; Jun-Wei Qiao; Xiao-Feng Niu; Bang-Shao Dong; Wei-Min Wang; Jing-Yu Qin

    2016-01-01

    We investigated structural disorder by a new structural parameter, quasi-nearest atom (QNA), in atomistic configurations of eight metallic glass-forming systems generated through molecular dynamics simulations at various temperatures. Structural analysis reveals that the scaled distribution of the number of QNA appears to be an universal property of metallic liquids and the spatial distribution of the number of QNA displays to be clearly heterogeneous. Furthermore, the new parameter can be di...

  11. Microstructure of Cu60Zr20Ti20 bulk metallic glass rolled at different strain rates

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The structural evolution of Cu60Zr20Ti20 bulk metallic glass during rolling at different strain rates and cryogenic temperature was investigated by X-ray diffraction (XRD),differential scanning calorimetry (DSC) and high-resolution transmission electron microscopy (HRTEM). It is revealed that the deformation-induced transformation is strongly dependent on the strain rate. At the lowest experimental strain rate of 1.0×10-4 s-1,no phase transformation occurs until the highest deformation degree reaches 95%. In a strain rate range of 5.0×10-4-5.0×10-2 s-1,phase separation oc-curs in a high deformation degree. As the strain rate reaches 5.0×10-1 s-1,phase separation and nanocrystallization concur. The critical deformation degree for oc-currence of phase transformation decreases with the strain rate increasing.

  12. Atomic interaction mechanism for designing the interface of W/Zr-based bulk metallic glass composites

    Science.gov (United States)

    Li, Z. K.; Fu, H. M.; Sha, P. F.; Zhu, Z. W.; Wang, A. M.; Li, H.; Zhang, H. W.; Zhang, H. F.; Hu, Z. Q.

    2015-03-01

    The interaction between active element Zr and W damages the W fibers and the interface and decreases the mechanical properties, especially the tensile strength of the W fibers reinforced Zr-based bulk metallic glass composites (BMGCs). From the viewpoint of atomic interaction, the W-Zr interaction can be restrained by adding minor elements that have stronger interaction with W into the alloy. The calculation about atomic interaction energy indicates that Ta and Nb preferred to segregate on the W substrate surface. Sessile drop experiment proves the prediction and corresponding in-situ coating appears at the interface. Besides, the atomic interaction mechanism was proven to be effective in many other systems by the sessile drop technique. Considering the interfacial morphology, Nb was added into the alloy to fabricate W/Zr-based BMGCs. As expected, the Nb addition effectively suppressed the W-Zr reaction and damage to W fibers. Both the compressive and tensile properties are improved obviously.

  13. Abrasive and corrosive behaviors of Cu-Zr-Al-Ag-Nb bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J L; Shek, C H [Department of Physics and Materials Science, City University of Hong Kong (Hong Kong); Lu, J X, E-mail: apchshek@cityu.edu.h

    2009-01-01

    The present work investigated effects of Nb (1-5 at.%) on CuZrAlAg bulk metallic glasses. The addition of Nb did not change the amorphous structure but affected the thermal behaviors significantly. The corrosion resistances of the BMGs with addition of 5 at% Nb in 0.5 N H{sub 2}SO{sub 4} solutions was the best among the samples. Pin-on-disk measurements showed that the hardest sample, viz. the one with 3 at% Nb exhibited the best wear resistance. Mechanical properties were also investigated using a nanoindentation technique. It was found that the addition of Nb may improved corrosion resistance and wear resistance of the Cu-based BMG, but not in a simple and systematic manner.

  14. The e/a criterion of Zr-based bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.M.; Xu, W.P.; Qiang, J.B.; Wong, C.H.; Shek, C.H.; Dong, C

    2004-07-15

    Bulk metallic glasses (BMGs) have been found in many Zr-based multi-component alloys. After discussions on the diffraction characteristics corresponding to the Fermi surfaces-Brillouin zone interaction effect in the Zr-based BMG-related phases, we point out that the 2k{sub f}{approx}k{sub p} rule is satisfied when the conduction electron concentration of Zr is 1.5. These BMG- and quasicrystal-related phases, sharing nearly the same conduction electron concentrations per atom (e/a), are e/a-constant phases in a given alloy system. Such an e/a-based criterion is then applied to the Zr-Al-Ni system and a series of BMGs with constant e/a ratio, equal to 1.5, are obtained by suction casting.

  15. Abrasive and corrosive behaviors of Cu-Zr-Al-Ag-Nb bulk metallic glasses

    Science.gov (United States)

    Zhang, J. L.; Lu, J. X.; Shek, C. H.

    2009-01-01

    The present work investigated effects of Nb (1-5 at.%) on CuZrAlAg bulk metallic glasses. The addition of Nb did not change the amorphous structure but affected the thermal behaviors significantly. The corrosion resistances of the BMGs with addition of 5 at% Nb in 0.5 N H2SO4 solutions was the best among the samples. Pin-on-disk measurements showed that the hardest sample, viz. the one with 3 at% Nb exhibited the best wear resistance. Mechanical properties were also investigated using a nanoindentation technique. It was found that the addition of Nb may improved corrosion resistance and wear resistance of the Cu-based BMG, but not in a simple and systematic manner.

  16. Deformation behavior of Fe-based bulk metallic glass during nanoindentation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Fe-based bulk metallic glasses (BMGs) normally exhibit super high strength but significant brittleness at ambient temperature. Therefore,it is difficult to investigate the plastic deformation behavior and mechanism in these alloys through conven-tional tensile and compressive tests due to lack of distinct macroscopic plastic strain. In this work,the deformation behavior of Fe52Cr15Mo9Er3C15B6 BMG was in-vestigated through instrumented nanoindentation and uniaxial compressive tests. The results show that serrated flow,the typical plastic deformation feature of BMGs,could not be found in as-cast and partially crystallized samples during nanoinden-tation. In addition,the deformation behavior and mechanical properties of the alloy are insensitive to the applied loading rate. The mechanism for the appearance of the peculiar deformation behavior in the Fe-based BMG is discussed in terms of the temporal and spatial characteristics of shear banding during nanoindentation.

  17. Deformation and failure of bulk metallic glasses under different initial temperatures

    Directory of Open Access Journals (Sweden)

    Li J.C.

    2015-01-01

    Full Text Available Based on the coupled thermo-mechanical model, a constitutive model for bulk metallic glasses (BMGs, which is generalized to the multi-axial stress state and considers the effects of free volume, heat and hydrostatic stress, has been modified in the present paper. Besides, a failure criterion of critical free volume concentration is introduced based on the coalescence mechanism of free volume. The constitutive model as well as the failure criterion is implemented into the LS-DYNA commercial software by user material subroutine (UMAT. Then FEM simulations for different initial material temperatures are conducted and the evolutions of material parameter as well as corresponding macroscopic mechanical behaviour of material are analyzed. Relative analysis shows that the initial material temperature significantly affects the deformation and failure of material.

  18. Deformation behavior of Fe-based bulk metallic glass during nanoindentation

    Institute of Scientific and Technical Information of China (English)

    LI Lei; LIU Yuan; ZHANG TaiHua; GU JianSheng; WEI BingChen

    2008-01-01

    Fe-based bulk metallic glasses (BMGs) normally exhibit super high strength but significant brittleness at ambient temperature. Therefore, it is difficult to investigate the plastic deformation behavior and mechanism in these alloys through conven-tional tensile and compressive tests due to lack of distinct macroscopic plastic strain. In this work, the deformation behavior of Fe52Cr15Mo9Er3C15B6 BMG was in-vestigated through instrumented nanoindentation and uniaxial compressive tests. The results show that serrated flow, the typical plastic deformation feature of BMGs, could not be found in as-cast and partially crystallized samples during nanoinden-tation. In addition, the deformation behavior and mechanical properties of the alloy are insensitive to the applied loading rate. The mechanism for the appearance of the peculiar deformation behavior in the Fe-based BMG is discussed in terms of the temporal and spatial characteristics of shear banding during nanoindentation.

  19. Deformation behavior during nanoindentation in Ce-based bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    ZHANG Lingchen; XING Dongmei; ZHANG Taihua; WEI Bingchen; LI Weihuo; WANG Yuren

    2006-01-01

    The deformation behavior and the effect of the loading rate on the plastic deformation in Ce-based bulk metallic glasses (BMGs) were investigated through nanoindentation tests. The results showed that the loading rate dependence of plastic deformation during nanoindentation measurements in the Ce-based BMGs is quite unique in contrast to that of other BMG alloys. The load-displacement (P-h)curves of Ce60Al15Cu10Ni15 BMG exhibit a homogeneous plastic deformation at low loading rates, and a prominent serrated flow at high strain rates, whereas,the P-h curves of Ce65Al10Cu10Ni10Nb5 exhibit homogenous plastic deformation at all studied loading rates. The room temperature creep behavior could clearly be observed in these two alloys. The mechanism of the unique plastic deformation feature in the Ce-based BMGs was studied.

  20. Correlation between atomic structure evolution and strength in a bulk metallic glass at cryogenic temperature.

    Science.gov (United States)

    Tan, J; Wang, G; Liu, Z Y; Bednarčík, J; Gao, Y L; Zhai, Q J; Mattern, N; Eckert, J

    2014-01-28

    A model Zr41.25Ti13.75Ni10Cu12.5Be22.5 (at.%) bulk metallic glass (BMG) is selected to explore the structural evolution on the atomic scale with decreasing temperature down to cryogenic level using high energy X-ray synchrotron radiation. We discover a close correlation between the atomic structure evolution and the strength of the BMG and find out that the activation energy increment of the concordantly atomic shifting at lower temperature is the main factor influencing the strength. Our results might provide a fundamental understanding of the atomic-scale structure evolution and may bridge the gap between the atomic-scale physics and the macro-scale fracture strength for BMGs.

  1. Crystallization of a Ti-based Bulk Metallic Glass Induced by Electropulsing Treatment

    Institute of Scientific and Technical Information of China (English)

    Yong-jiang HUANG; Xiang CHENG; Hong-bo FAN; Shi-song GUAN; Zhi-liang NING; Jian-fei SUN

    2016-01-01

    The effect of electropulsing treatment (EPT)on the microstructure of a Ti-based bulk metallic glass (BMG)has been studied.The maximum current density applied during EPT can exert a crucial role on tuning the microstructure of the BMG.When the maximum current density is no more than 2 720 A/mm2 ,the samples retains amorphous nature,whereas,beyond that,crystalline phases precipitate from the glassy matrix.During EPT,the maximum temperature within the samples EPTed at the maximum current densities larger than 2 720 A/mm2 is higher than the crystallization temperature of the BMG,leading to the crystallization event.

  2. Microstructural Analysis of a Laser-Processed Zr-Based Bulk Metallic Glass

    Science.gov (United States)

    Sun, H.; Flores, K. M.

    2010-07-01

    Laser processing is a precision manufacturing technique capable of producing materials with highly nonequilibrium microstructures. Due to the localized heat input and high cooling rate inherent to the process, this technology is attractive for the production of metallic glasses. In the present work, we use a laser deposition process to deposit a Zr-based metallic glass forming powder on both amorphous and crystalline substrates of the same nominal composition. Amorphous melt zones are observed surrounded by distinct crystalline heat-affected zones (HAZs). Detailed examination of the HAZ in the glassy substrates reveals the formation of microscale spherulites, in contrast to the nanocrystalline phases observed following crystallization by isothermal annealing of the glass at the crystallization temperature as well as in the HAZ of the crystalline substrates. The spherulites have a different crystal morphology and structure from the nanocrystalline phases, indicating that the more stable nanocrystalline phases are completely bypassed when the glass is devitrified at the higher heating rate. Reducing the heat input during laser processing results in the near elimination of the crystalline HAZ in the amorphous substrates, suggesting that a critical heating rate range is required to avoid devitrification.

  3. Influence of Cu content on the mechanical properties and corrosion resistance of Mg-Zn-Ca bulk metallic glasses

    Science.gov (United States)

    Zhao, Yan-feng; Zhu, Jian; Chang, Li; Song, Jing-guo; Chen, Xiao-hua; Hui, Xi-dong

    2014-05-01

    (Mg66.2Zn28.8Ca5)100- x Cu x (at%, x = 0, 1, 3, and 5) bulk metallic glasses (BMGs) of 2 mm in diameter were prepared by the conventional copper mold injection casting method. Besides, the influence of Cu content on the microstructure, thermal stability, mechanical properties, and corrosion behavior of Mg-Zn-Ca BMGs was investigated. It is found that the addition of Cu decreases the glass-forming ability of Mg-Zn-Ca BMGs. Crystalline phases are precipitated at a higher Cu content, larger than 3at%. The compressive fracture strength of Mg-Zn-Ca BMGs is enhanced by the addition of Cu. With the formation of in-situ composites, the compressive strength of the Mg-Zn-Ca alloy with 3at% Cu reaches 979 MPa, which is the highest strength among the Mg-Zn-Ca alloys. Furthermore, the addition of Cu also results in the increase of corrosion potential and the decrease of corrosion current density in Mg-Zn-Ca BMGs, thereby delaying their biodegradability.

  4. Corrosion of Biocompatible Mg66+xZn30-xCa4 (x=0.2 Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Nowosielski R.

    2016-06-01

    Full Text Available The aim of this paper was to investigate the corrosion resistance of Mg66Zn30Ca4 and Mg68Zn28Ca4 metallic glasses and evaluate the ability of this amorphous alloy use for medical applications as biodegradable medical implants. Taking into account the amount of Mg, Zn, Ca elements dissolved in multielectrolyte physiological fluid (MPF from Mg66+xZn30-xCa4 (x=0.2 alloys the daily dose of evolved ions from alloys components was determined. Additional goal of the paper was determination of corrosion rate (Vcorr and amount of hydrogen evolved from amorphous magnesium alloys in simulated environment of human body fluids during 24h immersion and during electrochemical tests. Corrosion studies were done in the multielectrolyte physiological fluid (MPF at 37°C. The amount of hydrogen evolved [ml/cm2] and corrosion rate Vcorr [mm/year] of amorphous Mg66Zn30Ca4 and Mg68Zn28Ca4 alloys were compared. The work also presents characterization of Mg-based bulk metallic glasses structure in the form of 2 mm thickness plates. Samples structure was analyzed by means of X-ray diffraction. Fracture and surface morphology of magnesium alloy samples were identified using scanning electron microscopy.

  5. In situ synthesis of TiC reinforced Cu47Ti34Zr11Ni8 bulk metallic glass composites

    Institute of Scientific and Technical Information of China (English)

    SUN Yufeng; ZHANG Guosheng; WEI Bingchen; LI Weihuo; WANG Yuren

    2004-01-01

    In situ synthesized TiC particles and β-Ti dendrites reinforced Cu47Ti34Zr11 Ni8 bulk metallic glass (BMG)composite ingots were prepared by the suction casting method. The ingots with diameters from 1 up to 4 mm were successfully obtained. It was shown that introducing TiC micro-sized particles into the amorphous matrix did not disturb the glass forming ability (GFA) of the matrix, while the yield strength and ductility could be well improved. The phase constitution, microstructure and elements distribution in the composites were studied by OM, XRD, SEM and EDS.It was shown that the in situ synthesized TiC particles acting as heterogeneous nucleation sites promoted the precipitation of β-Ti dendrites, resulting in the formation of the TiC particles and β-Ti dendrites co-reinforced BMG composites. The compressive tests were employed to probe the yield strength and ductility of BMG composites.

  6. Thermal Forming of Glass — Experiment vs. Simulation

    Directory of Open Access Journals (Sweden)

    L. Švéda

    2011-01-01

    Full Text Available Thermal forming is a technique for forming glass foils precisely into a desired shape. It is widely used in the automotive industry. It can also be used for shaping X-ray mirror substrates for space missions, as in our case. This paper presents the initial results of methods used for automatic data processing of in-situ measurements of the thermal shaping process and a comparison of measured and simulatated values. It also briefly describes improvements of the overall experimental setup currently being made in order to obtain better and more precise results.

  7. Electrical switching in bulk samples of 0. 15As-0. 12Ge-0. 73Te glass

    Energy Technology Data Exchange (ETDEWEB)

    Eckels, D.E.

    1976-06-01

    Switching in bulk samples of 0.15As--0.12Ge--0.73Te glass is found to be caused predominantly by the thermal switching mechanism for near threshold applied voltages. Switching also occurred by the thermal mechanism even for applied voltages an order of magnitude above the threshold voltage of the sample. In order to investigate a switching event in this glass sample, a constant voltage pulse was applied to the sample and the delay time and the electrical energy input to the sample during the delay time measured. A log--log plot of the energy input to the sample during a delay time of 1.00 s as a function of the electrode spacing on the sample's surface was found to have a slope of approximately 1.6. For the theoretical study of the thermal switching mechanism, a one-dimensional calculation of the heat balance equation with radial heat flow was made and the results of the calculation followed the same trends as the experimental data. The large scatter in parts of the data and the increase in the average resistance of the sample for a switching event with near threshold applied voltages could not be explained by the thermal switching mechanism. These effects could be a manifestation of the structural changes which probably occur in the sample as a result of the high temperatures present at the moment of switching. 33 fig.

  8. Dry Sliding Wear Behavior of Hafnium-Based Bulk Metallic Glass at Room and Elevated Temperatures

    Science.gov (United States)

    Keshri, Anup Kumar; Behl, Lovish; Lahiri, Debrupa; Dulikravich, George S.; Agarwal, Arvind

    2016-09-01

    Dry sliding wear behavior of hafnium-based bulk metallic glass was studied at two loads (5 and 15 N) and two temperatures (298 and 673 K) using aluminum oxide (Al2O3) ball as a wear counterpart. At 5 N load, wear reduced by ~71% on increasing the temperature from 298 to 673 K. At a higher load of 15 N, the weight loss reduction was much lower (45%) on increasing the temperature from 298 to 673 K. Decreased wear weight loss on increasing the temperature was attributed to the increased hardness of the Hf-based metallic glass at high temperatures. Micro-hardness of the alloy at 293 K was found to be 636 Hv, which gradually increased to 655 Hv on annealing at 673 K. Improvement in the hardness at elevated temperature is attributed to: (1) free volume annihilation, (2) surface oxide formation and (3) nano-crystallites precipitation. Reduced wear at elevated temperature resulted in smaller volume of debris generation that restricted three-body wear to obtain lower coefficient of friction (COF) (0.25-0.35) compared to COF (0.65-0.75) at room temperature.

  9. Phase formation and mechanical properties of Cu-Zr-Ti bulk metallic glass composites

    Science.gov (United States)

    Kim, Byoung Jin; Yun, Young Su; Kim, Won Tae; Kim, Do Hyang

    2016-11-01

    The effect of the type of the crystalline phase and its volume fraction on the mechanical property of Cu50Zr50-xTix alloys (x = 0-10) bulk metallic glass composites has been investigated in this study. Up to 6 at% of Ti, B19' phase particles distributed in the glassy matrix, while at 8 and 10% of Ti, B2 phase particles are retained in the glass matrix due to suppression of the eutectoid transformation of B2 phase and by avoidance of martensitic transformation of B2 into B19'. The volume fraction of crystalline phase is strongly dependent on the cooling rate. The larger volume fraction of the crystalline phases results in the lower yield stress, the higher plastic strain, and the more pronounced work hardening behavior. At the crystalline volume fraction below 30%, the variation of the yield strength can be described by the rule of mixture model (ROM), while at the crystalline volume fraction higher than 50% by the load-bearing model (LBM). At the crystal fractions between 30 and 50%, there is a yield strength drop and a transition from the ROM to the LBM. This transition is due to the formation of the crystalline structural framework at higher crystal fraction.

  10. Mechanical Properties, Damage and Fracture Mechanisms of Bulk Metallic Glass Materials

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The deformation, damage, fracture, plasticity and melting phenomenon induced by shear fracture were investigated and summarized for Zr-, Cu-, Ti- and Mg-based bulk metallic glasses (BMGs) and their composites. The shear fracture angles of these BMG materials often display obvious differences under compression and tension,and follow either the Mohr-Coulomb criterion or the unified tensile fracture criterion. The compressive plasticity of the composites is always higher than the tensile plasticity, leading to a significant inconsistency. The enhanced plasticity of BMG composites containing ductile dendrites compared to monolithic glasses strongly depends on the details of the microstructure of the composites. A deformation and damage mechanism of pseudo-plasticity, related to local cracking, is proposed to explain the inconsistency of plastic deformation under tension and compression. Besides, significant melting on the shear fracture surfaces was observed. It is suggested that melting is a common phenomenon in these materials with high strength and high elastic energy, as it is typical for BMGs and their composites failing under shear fracture. The melting mechanism can be explained by a combined effect of a significant temperature rise in the shear bands and the instantaneous release of the large amount of elastic energy stored in the material.

  11. Glass transition of polymers in bulk, confined geometries, and near interfaces

    Science.gov (United States)

    Napolitano, Simone; Glynos, Emmanouil; Tito, Nicholas B.

    2017-03-01

    When cooled or pressurized, polymer melts exhibit a tremendous reduction in molecular mobility. If the process is performed at a constant rate, the structural relaxation time of the liquid eventually exceeds the time allowed for equilibration. This brings the system out of equilibrium, and the liquid is operationally defined as a glass—a solid lacking long-range order. Despite almost 100 years of research on the (liquid/)glass transition, it is not yet clear which molecular mechanisms are responsible for the unique slow-down in molecular dynamics. In this review, we first introduce the reader to experimental methodologies, theories, and simulations of glassy polymer dynamics and vitrification. We then analyse the impact of connectivity, structure, and chain environment on molecular motion at the length scale of a few monomers, as well as how macromolecular architecture affects the glass transition of non-linear polymers. We then discuss a revised picture of nanoconfinement, going beyond a simple picture based on interfacial interactions and surface/volume ratio. Analysis of a large body of experimental evidence, results from molecular simulations, and predictions from theory supports, instead, a more complex framework where other parameters are relevant. We focus discussion specifically on local order, free volume, irreversible chain adsorption, the Debye–Waller factor of confined and confining media, chain rigidity, and the absolute value of the vitrification temperature. We end by highlighting the molecular origin of distributions in relaxation times and glass transition temperatures which exceed, by far, the size of a chain. Fast relaxation modes, almost universally present at the free surface between polymer and air, are also remarked upon. These modes relax at rates far larger than those characteristic of glassy dynamics in bulk. We speculate on how these may be a signature of unique relaxation processes occurring in confined or heterogeneous polymeric

  12. Influence of the Ag concentration on the medium-range order in a CuZrAlAg bulk metallic glass

    Science.gov (United States)

    Gammer, C.; Escher, B.; Ebner, C.; Minor, A. M.; Karnthaler, H. P.; Eckert, J.; Pauly, S.; Rentenberger, C.

    2017-03-01

    Fluctuation electron microscopy of bulk metallic glasses of CuZrAl(Ag) demonstrates that medium-range order is sensitive to minor compositional changes. By analyzing nanodiffraction patterns medium-range order is detected with crystal-like motifs based on the B2 CuZr structure and its distorted structures resembling the martensitic ones. This result demonstrates some structural homology between the metallic glass and its high temperature crystalline phase. The amount of medium-range order seems slightly affected with increasing Ag concentration (0, 2, 5 at.%) but the structural motifs of the medium-range ordered clusters become more diverse at the highest Ag concentration. The decrease of dominant clusters is consistent with the destabilization of the B2 structure measured by calorimetry and accounts for the increased glass-forming ability.

  13. Pressure effect of glass transition temperature in Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk metallic glass

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Roseker, W.; Sikorski, M.

    2004-01-01

    Pressure effects on glass transition temperature and supercooled liquid region of a Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass have been investigated by performing in situ high-temperature and high-pressure x-ray powder diffraction measurements using synchrotron radiation. The glass transition...... was detected from the change of the slope of peak position as a function of temperature. It is found that the glass transition temperature increases with pressure by 4.4 K/GPa for the Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass, and the supercooled liquid range decreases with pressure by 2.9 K/GPa in a pressure...... range of 0-2.2 GPa. This method opens a possibility to study the pressure effect of glass transition process in glassy systems under high pressures (>1 GPa). (C) 2004 American Institute of Physics....

  14. Non-Local Ductile Damage Formulations for Sheet Bulk Metal Forming

    Science.gov (United States)

    Beese, Steffen; Loehnert, Stefan; Wriggers, Peter

    2016-08-01

    A ductile damage model for sheet bulk metal forming processes and its efficient and accurate treatment in the context of the Finite Element Method is presented. The damage is introduced as a non-local field to overcome pathological mesh dependency. Since standard elements tend to show volumetric locking in the bulk forming process a mixed formulation is implemented in the commercial software simufact.forming to obtain better results.

  15. Direct observation of bulk second-harmonic generation inside a glass slide with tightly focused optical fields

    Science.gov (United States)

    Wang, Xianghui; Fardad, Shima; Das, Susobhan; Salandrino, Alessandro; Hui, Rongqing

    2016-04-01

    Bulk second-harmonic generation (SHG) inside glass slides is directly detected unambiguously without interference from surface contributions. This is enabled by tightly focused and highly localized ultrashort laser pulses. The theoretical calculations based on vector diffraction theory and the phenomenological model of SHG inside centrosymmetric materials agree well with the measured far-field SHG radiation patterns for different polarization states of the fundamental beam. The results indicate that the observed bulk SHG is predominantly related to the bulk parameter δ' and originates from the three-dimensional field gradient in the focal region.

  16. Precision analysis in billet preparation for micro bulk metal forming

    DEFF Research Database (Denmark)

    Mahshid, Rasoul; Hansen, Hans N.

    2015-01-01

    press. When using a vertical mechanical press, the material is fed as billets into the forming zone. Therefore, a large number of highly uniform billets are required to run mass production in such a setup. Shearing technique was used for manufacturing the billets. The efficiency of the shearing tool...... is examined in terms of volume control, circularity, dimension and sheared surface quality. The shearing tool is based on holders for both bar and cutoff. The tool is fixed in dimensions, since the dimensions of billets are fixed throughout experiments of this research. The paper presents the experimental...

  17. Electron-band theory inspired design of magnesium-precious metal bulk metallic glasses with high thermal stability and extended ductility.

    Science.gov (United States)

    Laws, Kevin J; Shamlaye, Karl F; Granata, Davide; Koloadin, Leah S; Löffler, Jörg F

    2017-06-13

    Magnesium-based bulk metallic glasses (BMGs) exhibit high specific strengths and excellent glass-forming ability compared to other metallic systems, making them suitable candidates for next-generation materials. However, current Mg-based BMGs tend to exhibit low thermal stability and are prone to structural relaxation and brittle failure. This study presents a range of new magnesium-precious metal-based BMGs from the ternary Mg-Ag-Ca, Mg-Ag-Yb, Mg-Pd-Ca and Mg-Pd-Yb alloy systems with Mg content greater than 67 at.%. These alloys were designed for high ductility by utilising atomic bond-band theory and a topological efficient atomic packing model. BMGs from the Mg-Pd-Ca alloy system exhibit high glass-forming ability with critical casting sizes of up to 3 mm in diameter, the highest glass transition temperatures (>200 °C) of any reported Mg-based BMG to date, and sustained compressive ductility. Alloys from the Mg-Pd-Yb family exhibit critical casting sizes of up to 4 mm in diameter, and the highest compressive plastic (1.59%) and total (3.78%) strain to failure of any so far reported Mg-based glass. The methods and theoretical approaches presented here demonstrate a significant step forward in the ongoing development of this extraordinary class of materials.

  18. Mechanically driven phase separation and corresponding microhardness change in Cu60Zr20Ti20 bulk metallic glass

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Zhou, Y.H.

    2005-01-01

    Rolling deformation of bulk Cu60Zr20Ti20 metallic glass has been performed at cryogenic temperature. The specimens exhibit excellent ductility, and are rolled up to 97% reduction in thickness without fracture. Crystallization is suppressed during the deformation, however, phase separation...

  19. Free-volume evolution and its temperature dependence during rolling of Cu60Zr20Ti20 bulk metallic glass

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Zhou, Y.H.

    2005-01-01

    The free-volume evolution during rolling Cu60Zr20Ti20 bulk metallic glass at room and cryogenic temperatures has been investigated by differential scanning calorimetry. When the specimen is rolled at cryogenic temperature, the free-volume content increases as the rolling proceeds first...

  20. In vitro and in vivo studies on biodegradable CaMgZnSrYb high-entropy bulk metallic glass.

    Science.gov (United States)

    Li, H F; Xie, X H; Zhao, K; Wang, Y B; Zheng, Y F; Wang, W H; Qin, L

    2013-11-01

    In order to enhance the corrosion resistance of the Ca65Mg15Zn20 bulk metallic glass, which has too fast a degradation rate for biomedical applications, we fabricated the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass because of the unique properties of high-entropy alloys. Our results showed that the mechanical properties and corrosion behavior were enhanced. The in vitro tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass could stimulate the proliferation and differentiation of cultured osteoblasts. The in vivo animal tests showed that the Ca20Mg20Zn20Sr20Yb20 high-entropy bulk metallic glass did not show any obvious degradation after 4 weeks of implantation, and they can promote osteogenesis and new bone formation after 2 weeks of implantation. The improved mechanical properties and corrosion behavior can be attributed to the different chemical composition as well as the formation of a unique high-entropy atomic structure with a maximum degree of disorder.

  1. Effect of rolling deformation on the microstructure of bulk Cu60Zr20Ti20 metallic glass and its crystallization

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Zhou, Y.H.;

    2006-01-01

    Bulk Cu60Zr20Ti20 metallic glass has been rolled at room temperature (RT) and cryogenic temperature (CIF) up to 97% in thickness reduction, and the dependences of microstructure on the strain and temperature have been investigated. It is revealed that as the deformation proceeds below a critical...

  2. Influence of pulsing current on the glass transition and crystallizing kinetics of a Zr base bulk amorphous alloy

    Institute of Scientific and Technical Information of China (English)

    WU Wenfei; YAO Kefu; ZHAO Zhankui

    2004-01-01

    Based on the thermal analysis, the influence of pulsing current on the glass transition and crystallizing kinetics of Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy has been studied. The obtained results show that after the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy was pretreated by high-density pulsing current at low temperature, its glass transition temperature Tg, the initial crystallizing temperature Tx and the corresponding exothermic peak of crystallization Tpi were reduced. But the temperature range of supercooled liquid ΔT=Tx-Tg is almost the same. The calculated results with Kissinger equation show that the activation energy of glass transition of the alloy pretreated is reduced significantly, while the activation energy of crystallization is basically unchanged. The influence of pulsing current on the glass transition and crystallization of the Zr41.3Ti14.2Cu12.8Ni10.3Be21.4 bulk amorphous alloy is believed to be related with the structure relaxation of the glass caused by the current.

  3. Microcraters formed in glass by low density projectiles

    Science.gov (United States)

    Mandeville, J.-C.; Vedder, J. F.

    1971-01-01

    Microcraters were produced in soda-lime glass by the impact of low density projectiles of polystyrene with masses between 0.7 and 62 picograms and velocities between 2 and 14 kilometers per second. The morphology of the craters depends on the velocity and angle of incidence of the projectiles. The transitions in morphology of the craters formed by polystyrene spheres occur at higher velocities than they do for more dense projectiles. For oblique impact, the craters are elongated and shallow with the spallation threshold occuring at higher velocity. For normal incidence, the total displaced mass of the target material per unit of projectile kinetic energy increases slowly with the energy.

  4. Accuracy of a selection criterion for glass forming ability in the Ni–Nb–Zr system

    Energy Technology Data Exchange (ETDEWEB)

    Déo, L.P., E-mail: leonardopratavieira@gmail.com; Oliveira, M.F. de, E-mail: falcao@sc.usp.br

    2014-12-05

    Highlights: • We applied a selection in the Ni–Nb–Zr system to find alloys with high GFA. • We used the thermal parameter γ{sub m} to evaluate the GFA of alloys. • The correlation between the γ{sub m} parameter and R{sub c} in the studied system is poor. • The effect of oxygen impurity reduced dramatically the GFA of alloys. • Unknown intermetallic compounds reduced the accuracy of the criterion. - Abstract: Several theories have been developed and applied in metallic systems in order to find the best stoichiometries with high glass forming ability; however there is no universal theory to predict the glass forming ability in metallic systems. Recently a selection criterion was applied in the Zr–Ni–Cu system and it was found some correlation between experimental and theoretical data. This criterion correlates critical cooling rate for glass formation with topological instability of stable crystalline structures; average work function difference and average electron density difference among the constituent elements of the alloy. In the present work, this criterion was applied in the Ni–Nb–Zr system. It was investigated the influence of factors not considered in the calculation and on the accuracy of the criterion, such as unknown intermetallic compounds and oxygen contamination. Bulk amorphous specimens were produced by injection casting. The amorphous nature was analyzed by X-ray diffraction and differential scanning calorimetry; oxygen contamination was quantified by the inert gas fusion method.

  5. Crystallization of Pd40CU30Ni10P20 bulk metallic glass with and without pressure

    DEFF Research Database (Denmark)

    Yang, B.; Jiang, Jianzhong; Zhuang, Yanxin;

    2007-01-01

    The glass-transition behavior of Pd40Cu30Ni10P20 bulk metallic glass was investigated by differential scanning calorimetry (DSC) and X-ray powder diffraction (XRD). The effect of pressure on the crystallization behavior of Pd40Cu30Ni10P20 bulk glass was studied by in situ high-pressure and high......-temperature X-ray powder diffraction using synchrotron radiation. Phase analyses show at least six crystalline phases in the crystallized sample, namely, monoclinic, tetragonal Cu3Pd-like, rhombohedral, fcc-Ni2Pd2P, fcc-(Ni, Pd) solid solution, and body-centered tetragonal (bct) Ni3P-like phases. The onset...... crystallization temperature increases with pressure having a slope of I I K/GPa in the range of 0 to 4 GPa. The results are attributed to the competing process between the thermodynamic potential barrier and the diffusion activation energy under pressure....

  6. A Series of Zr-Based Bulk Metallic Glasses with Room Temperature Plasticity

    Directory of Open Access Journals (Sweden)

    Anhui Cai

    2016-05-01

    Full Text Available A group of plastic Zr-Al-Ni-Cu bulk metallic glasses (BMGs with low Zr content was developed and their thermal and mechanical properties were investigated. The results show that these Zr-based BMGs have a single crystallization event for all heating rates in the studied temperature region. The glass transition temperature Tg decreases with increasing Zr content for all heating rates. There are two melting procedures for the BMGs whose Zr content is less than 52 at %, while three melting procedures for the other Zr-based BMGs. The second melting procedure is split into two melting procedures for Zr52.5Al12.2Ni12.6Cu22.7 and Zr53Al11.6Ni11.7Cu23.7 BMGs, while the first melting procedure is split into two melting procedures for the other BMGs. The activation energy decreases with increasing sensitivity index β for the studied Zr-based BMGs. The plastic strain εp is in the region of 0.2%–19.1% for these Zr-based BMGs. Both yield strength σy and fracture strength σf are smallest for Zr55Al8.9Ni7.3Cu28.8 BMG whose εp is largest among all studied Zr-based BMGs and reaches up to 19.1%. In addition, the mechanism for the large difference of the plasticity among the studied Zr-based BMGs is also discussed.

  7. Domain structure of hard magnetic NdAIFeCo bulk metallic glass

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Magnetic domain structure of hard magnetic Nd60Al10Fe20Co10 bulk metallic glass (BMG) has been studied by using magnetic force microscopy. In the magnetic force images it is shown that the exchange interaction type mag netic domains with a period of about 360 nm do exist in the BMG, which is believed to be associated with the appearance of hard-magnetic properties in this system. As the scale of the magnetic domain is much larger than the size of the short-range ordered atomic clusters existing in the BMG, it is believed that the large areas of magnetic contrast are actu ally a collection of a group of clusters aligned in parallel by strong exchange coupling interaction. After fully crystalliza tion, the BMG exhibits paramagnetism. No obvious magnetic contrast is observed in the magnetic force images of fully crystallized samples, except for a small quantity of ferro magnetic crystalline phase with low coercivity and an average size of 900 nm.

  8. The Evolution of Microstructures and the Properties of Bulk Metallic Glass with Consubstantial Composition Laser Welding

    Directory of Open Access Journals (Sweden)

    Pingjun Tao

    2016-09-01

    Full Text Available A Zr55Cu30Ni5Al10 plate-like bulk metallic glass (BMG was prepared using copper mold suction casting. Additionally, alloy powders with the same nominal composition were synthesized. The alloy powders were welded or melted to the cleaned surface of the BMG with a laser beam acceleration voltage of 60 kV, a beam current range from 60 to 100 mA, a welding speed of 60 mm/s, as well as an impulse width of 3.0 ms. The effect of consubstantial composition welding on the microstructures and properties was investigated. The molten and subsequently solidified metallic mixtures remain an amorphous structure, but the enthalpy of the welded or melted position varies due to the combination of the micro-structural relaxation and nano-crystals precipitated during the energy inputs. The surface layers of the BMG can be significantly intensified after welding processes; however, the heat-affected zones (HAZs exhibit a slight degradation in mechanical properties with respect to the BMG matrix. This study has important reference value for specialists working on the promotion of applications of BMGs.

  9. Experimental evidence for both progressive and simultaneous shear during quasistatic compression of a bulk metallic glass

    Science.gov (United States)

    Wright, Wendelin J.; Liu, Yun; Gu, Xiaojun; Van Ness, Katherine D.; Robare, Steven L.; Liu, Xin; Antonaglia, James; LeBlanc, Michael; Uhl, Jonathan T.; Hufnagel, Todd C.; Dahmen, Karin A.

    2016-02-01

    Two distinct types of slip events occur during serrated plastic flow of bulk metallic glasses. These events are distinguished not only by their size but also by distinct stress drop rate profiles. Small stress drop serrations have fluctuating stress drop rates (with maximum stress drop rates ranging from 0.3-1 GPa/s), indicating progressive or intermittent propagation of a shear band. The large stress drop serrations are characterized by sharply peaked stress drop rate profiles (with maximum stress drop rates of 1-100 GPa/s). The propagation of a large slip is preceded by a slowly rising stress drop rate that is presumably due to the percolation of slipping weak spots prior to the initiation of shear over the entire shear plane. The onset of the rapid shear event is accompanied by a burst of acoustic emission. These large slips correspond to simultaneous shear with uniform sliding as confirmed by direct high-speed imaging and image correlation. Both small and large slip events occur throughout plastic deformation. The significant differences between these two types require that they be carefully distinguished in both modeling and experimental efforts.

  10. Serrated flow behaviors of a Zr-based bulk metallic glass by nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, L.; Jiao, Z. M.; Ma, S. G.; Wang, Z. H., E-mail: qiaojunwei@gmail.com, E-mail: wangzhihua@tyut.edu.cn [Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Qiao, J. W., E-mail: qiaojunwei@gmail.com, E-mail: wangzhihua@tyut.edu.cn [Institute of Applied Mechanics and Biomedical Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Laboratory of Applied Physics and Mechanics of Advanced Materials, College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024 (China)

    2014-02-28

    Instrumented nanoindentation tests were used to investigate the mechanical properties of Zr{sub 52.5}Cu{sub 17.9}Ni{sub 14.6}Al{sub 10}Ti{sub 5} bulk metallic glass. The corresponding loading strain rates were ranged from 0.002 s{sup −1}, 0.02 s{sup −1} to 0.2 s{sup −1}. Plastic flow of this material exhibited remarkable serrations at low strain rates and increasingly became weakening until disappearance with increasing indentation strain rate, implying strong rate sensitivity. A significant pile-up around the indents was observed through atomic force microscopy, which suggested a highly localized plastic deformation. Mechanism governing the deformation was tentatively discussed in terms of the increasing process of free volume with a negligible temperature rise under low strain rate, which well explained the declining trend of elastic modulus and hardness with an increase of indentation depth.

  11. Plastic deformation behavior of Fe–Co–B–Si–Nb–Cr bulk metallic glasses under nanoindentation

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.T.; Hong, S.H.; Lee, C.H. [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Park, J.M., E-mail: jinman_park@hotmail.com [Materials Research Center, Samsung Advanced Institute of Technology (SAIT), San 14-1, Nongseo-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-712 (Korea, Republic of); Kim, T.W.; Lee, W.H. [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of); Yim, H.I. [Department of Physics, Sookmyung Women’s University, Hyochangwongil 52, Yongsan-ku, Seoul 140-742 (Korea, Republic of); Kim, K.B., E-mail: kbkim@sejong.ac.kr [HMC, Faculty of Nanotechnology and Advanced Materials Engineering, Sejong University, 98 Gunja-dong, Gwangjin-gu, Seoul 143-747 (Korea, Republic of)

    2014-02-25

    Highlights: • Additional Cr modulation of atomic structure of Fe-Co-B-Si-Nb BMGs. • An amount of free volume characterized by a combination of nanoindentation and AFM. • Free volume determined by height measurement of AFM after nanoindentation. -- Abstract: In this work, we investigate the effect of Cr addition on thermal properties and indentation behavior of Fe{sub 52}Co{sub 20−x}B{sub 20}Si{sub 4}Nb{sub 4}Cr{sub x} alloys with x = 0, 1, 3 and 5 at.%, respectively. Among all studied alloys, the Fe{sub 52}Co{sub 17}B{sub 20}Si{sub 4}Nb{sub 4}Cr{sub 3} bulk metallic glass (BMG) exhibits the highest thermal stability with large supercooled liquid region of 40 K and the pronounced plastic deformation features which is serrated flow (pop-in event) and significant pile-up of materials around indents. This demonstrates that the appropriate addition of Cr in Fe-based BMG can induce the internal atomic structure modulation and promote the mechanical softening, which are discussed in terms of free volume concept.

  12. Mapping the Strain Distributions in Deformed Bulk Metallic Glasses Using Hard X-Ray Diffraction

    Science.gov (United States)

    Bednarcik, J.; Chen, L. Y.; Wang, X. D.; Jiang, J. Z.; Franz, H.

    2012-05-01

    The deformation behavior of Cu45 Zr46.5 Al7Ti1.5 bulk metallic glass (BMG) under bending was investigated in-situ using high-energy X-ray synchrotron diffraction. Samples were bent using two different benders with radii of 10 and 20 mm. The components of the strain tensor were determined from the change of positions of the first maximum of the diffracted intensity in reciprocal space. The procedure of data treatment was improved by the introduction of direct beam off-center correction. Comparing results for the two different bending radii, we found that the zero stress region does not necessarily lay within the central part of the specimen. Bending with smaller radius resulted in symmetric strain distribution, whereas a larger bending radius revealed strong asymmetry. Furthermore, bending with a smaller radius (10 mm) shows steeper strain gradients as compared with the situation in which the larger bending radius (20 mm) was used. Using a smaller bending radius implies reaching higher tensile/compressive stresses and reveals the signs of the plastic deformation, which are demonstrated as a saturation of elastic strains.

  13. Mechanisms of compressive deformation and failure of porous bulk metallic glasses

    Science.gov (United States)

    Gouripriya, S.; Tandaiya, Parag

    2017-06-01

    Bulk metallic glasses (BMGs) are a new class of engineering materials having strengths as high as 10 times that of conventional steels, but show no significant plastic strain at fracture. By introducing pores, their strain to failure has been shown to improve under uniaxial compression. In this work, three-dimensional finite element simulations of uniaxial compression are carried out on Pd-based porous BMGs having a wide range of pore volume fraction (1.9%-60%) with emphasis on understanding the underlying deformation and failure mechanisms. The resulting stress-strain curves agree reasonably well with existing experimental results. The simulations clearly bring out different failure mechanisms in low porosity BMGs and high porosity BMG foams. For low porosity BMGs (below 20%), the deformation and failure involves nucleation of shear bands around the pore diameter, linking of the shear bands with adjacent pores finally leading to initiation of ductile cracking within the shear bands. For high porosity BMG foams, the mechanism of deformation involves reduction in porosity of the material, self-contact of the pores, and their collapse on themselves causing densification of the material leading to apparent hardening in the stress strain behavior. The effect of pore geometry is also studied by considering ellipsoidal pores of volume fraction 3% and 11%. For ellipsoidal pores, the failure mechanisms are found to differ significantly when the orientation of the major axis of the pore vis-a-vis the loading axis is changed.

  14. Local melting to design strong and plastically deformable bulk metallic glass composites

    Science.gov (United States)

    Qin, Yue-Sheng; Han, Xiao-Liang; Song, Kai-Kai; Tian, Yu-Hao; Peng, Chuan-Xiao; Wang, Li; Sun, Bao-An; Wang, Gang; Kaban, Ivan; Eckert, Jürgen

    2017-02-01

    Recently, CuZr-based bulk metallic glass (BMG) composites reinforced by the TRIP (transformation-induced plasticity) effect have been explored in attempt to accomplish an optimal of trade-off between strength and ductility. However, the design of such BMG composites with advanced mechanical properties still remains a big challenge for materials engineering. In this work, we proposed a technique of instantaneously and locally arc-melting BMG plate to artificially induce the precipitation of B2 crystals in the glassy matrix and then to tune mechanical properties. Through adjusting local melting process parameters (i.e. input powers, local melting positions, and distances between the electrode and amorphous plate), the size, volume fraction, and distribution of B2 crystals were well tailored and the corresponding formation mechanism was clearly clarified. The resultant BMG composites exhibit large compressive plasticity and high strength together with obvious work-hardening ability. This compelling approach could be of great significance for the steady development of metastable CuZr-based alloys with excellent mechanical properties.

  15. Examination of Galvanic Action between Fe-Based Bulk Metallic Glass and Crystalline Alloys

    Science.gov (United States)

    Ha, Hung M.; Payer, Joe H.

    2009-06-01

    Fe-based bulk metallic glasses (amorphous metals) have been developed, and several compositions are shown to have excellent corrosion resistance in chloride solutions. Further, thermal-spray amorphous metals are being developed for use as a barrier coating layer, to protect substrate materials from corrosion. Galvanic action between dissimilar metals and the coating/substrate for the amorphous-alloy coatings is of practical interest for a number of applications. The mixed-potential theory provides a useful approach for examining the corrosion behavior of the component materials in the galvanic couple and is applied in this study. Galvanic action was studied for an Fe-based structurally amorphous metal (SAM) 1651 and several crystalline alloys that included 1018 C-steel, stainless steel (SS) 316L, and alloy 22. Anodic and cathodic polarization curves of each of the metals were measured by potentiodynamic polarization. Based on the mixed-potential theory, the behavior of the component materials in a galvanic cell was predicted. The predictions are compared to the measured behavior of galvanic couples with the crystalline alloys.

  16. Structural and mechanical modifications induced on Zr-based bulk metallic glass by laser shock peening

    Science.gov (United States)

    Zhu, Yunhu; Fu, Jie; Zheng, Chao; Ji, Zhong

    2016-12-01

    In this study, surface modification of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 (vit1) bulk metallic glass (BMG) has been studied in an effort to improve the mechanical properties by laser shock peening (LSP) treatment. The phase structure, mechanical properties, and microstructural evolution of the as-cast and LSP treated specimens were systematically investigated. It was found that the vit1 BMG still consisted of fully amorphous structure after LSP treatment. Measurements of the heat relaxation indicate that a large amount of free volume is introduced into vit1 BMG during LSP process. LSP treatment causes a decrease of hardness attributable to generation of free volume. The plastic deformation ability of vit1 BMG was investigated under three-point bending conditions. The results demonstrate that the plastic strain of LSP treated specimen is 1.83 times as large as that of the as-cast specimen. The effect of LSP technology on the hardness and plastic deformation ability of vit1 BMG is discussed on the basis of free volume theory. The high dense shear bands on the side surface, the increase of striations and critical shear displacement on the tensile fracture region, and more uniform dimples structure on the compressive fracture region also demonstrate that the plasticity of vit1 BMG can be enhanced by LSP.

  17. Wear behaviour of Zr-based in situ bulk metallic glass matrix composites

    Indian Academy of Sciences (India)

    X F WU; G A ZHANG; F F WU

    2016-06-01

    Zr-based bulk metallic glass (BMG) and its in situ BMG matrix composites with diameter of 3 mm were fabricated by conventional Cu-mould casting method and the dry sliding wear behaviour of the BMG and composites was investigated. Compared to the pure BMG, the composites exhibited a markedly improved wear resistance from 10 to 48% due to the existence of various volume fractions of the ductile $\\beta$-Zr dendritic phase embedded in the glassy matrix. The composites showed lower friction coefficient and wear rate than the pure BMG. Meanwhile, the surface wearing of the composite with a proper amount of $\\beta$-Zr dendrites was less severe compared to that of the pure BMG. The worn surface of the composite was covered with mild grooves and some fine wear debris, which exhibited the characteristic of a mild abrasive wear. The improvement of the wear resistance of the composite with the proper amount of $\\beta$-Zr crystalline phase is attributed to the fact that the $\\beta$-Zr crystalline phase distributed in the amorphous matrix has some effective load bearing, plastic deformation and work hardening ability to decrease strain accumulation and the release of strain energy in the glassy matrix, restrict the expanding of shear bands and cracks, and occur plastic deformation homogeneously.

  18. TOPICAL REVIEW On the glass forming ability of liquid alloys

    Directory of Open Access Journals (Sweden)

    Yoshio Waseda et al

    2008-01-01

    Full Text Available By using the concepts of the short-range order (SRO and middle-range order (MRO characterizing structures, an attempt has been made to describe the glass forming ability (GFA of liquid alloys. This includes the effect of more than two kinds of SRO in the liquid caused by the addition of second and third elements to a metallic solvent. The minimum solute concentration is related to the atomic volume mismatch estimated from the cube of the atomic radius. The optimum solute concentration for good glass formability in several binary and some ternary alloys is discussed on the basis of the empirical guideline. A new approach to obtaining good GFA of liquid alloys is based on four main factors: (i formation of new SRO and coexistence of two or more kinds of SRO, (ii stabilization of dense random packing structure by restraining the atomic redistribution for initiating the nucleation and growth process, (iii formation of a stable cluster (SC or the MRO by the harmonious coupling of SROs, and (iv difference between SRO characterizing the liquid structure and the near-neighbor environment in the corresponding equilibrium crystalline phases. The use of interaction parameters, widely used in the thermodynamics of multicomponent metallic solutions, is proposed for effectively selecting the third solute element (X3 for enhancing the GFA of a metallic liquid (M containing the second solute (X2. Fe70-B20-(X310 alloys (X3=Cr, W, Nb, Zr and Hf are used for illustration. Two typical model structures denoted by the Bernal and chemical-order types are used in describing the new glass structure as a function of solute concentration.

  19. A Kinetic Study of the Non-isothermal Crystallization of a Zr-Based Bulk Metallic Glass

    Institute of Scientific and Technical Information of China (English)

    柳林; 吴志方; 陈莉

    2002-01-01

    The kinetics of the non-isothermal crystallization ofZr55 Cu30Al10Ni5 bulk metallic glass was studied by differentialscanning calorimetry in the mode of continuous heating. It is found that both glass transition and crystallizationof the amorphous alloy behave in a marked kinetic nature. The activation energy E and frequency factor c0 forcrystallization were determined by the Kissinger method, which yields E = 230 kJ/mol, and k0 = 4.2 × l0Ca/s.The value of k0 is much smaller than that for conventional amorphous alloys, demonstrating that the atomicmobility in bulk metallic glasses is quite sluggish. The crystallization mechanism in the non-isothermal processwas analysed in terms of the kinetic transformation equation for the solid-state phase transformation. Thisreveals that the crystallization kinetic function f (x) for Zr55 Cu30Al10Ni5 can be described by the Johnson-Mehl-Avrami equation, i.e. f(x) = (1 - x)[- ln(1 - x)](n-1)/n, with n = 1.75. This indicates that the non-isothermalcrystallization of Zr55 Cu30Al10Ni5 bulk metallic glass is governed by diffusion-controlled one-dimensional growth.Finally, the different crystallization mechanisms in the isothermal and non-isothermal processes are discussed.

  20. Lasing effects in new Nd3+-doped TeO2-Nb2O5-WO3 bulk glasses

    Science.gov (United States)

    Carreaud, J.; Labruyère, A.; Dardar, H.; Moisy, F.; Duclère, J.-R.; Couderc, V.; Bertrand, A.; Dutreilh-Colas, M.; Delaizir, G.; Hayakawa, T.; Crunteanu, A.; Thomas, P.

    2015-09-01

    This paper demonstrates for the first time continuous wave (cw) and pulsed lasing effects in a 75TeO2-20NbO2.5-5WO3 glass doped with 1 mol.% in Nd3+. It is divided into two parts: The first part treats all the aspects related to the elaboration and the characterization of the materials. Thus, glasses elaborated within the TeO2-Nb2O5-WO3 ternary system show a rather high glass transition temperature Tg ∼ 375 °C, with an excellent thermal stability of ∼160 °C. Compared to glasses synthesized in either TeO2-Nb2O5 or TeO2-WO3 binary systems, glasses fabricated within such system show improved mechanical performances, with larger Young's modulus values. The structural characteristics of the samples, studied by Raman spectroscopy, are also presented. Linear optical properties (refractive index and extinction coefficient) are accessed by spectroscopic ellipsometry. As well, the optical transmission of the various bulk glasses is measured, in the case of both uncoated and coated glasses. In particular, specific anti-reflective coatings at 808 nm (laser diode pump wavelength) and 1064 nm (laser emission wavelength) are respectively deposited on the two surfaces of the sample in order to minimize the losses due to Fresnel reflections at the two glass/air interfaces. In addition, another specific surface treatment (Rmax at 1064 nm) was employed to serve as the back mirror of the laser cavity. The optical transmission data testified to the real efficiency of all these coatings. Finally, the photoluminescence properties (emission and excitation spectra, and luminescence decay curve) of the Nd3+-doped glasses, measured at room temperature for bulk samples, and as a function of temperature for powder glasses, are discussed. The second part is focused on evidencing (cw) and pulsed lasing effects in such coated bulk lasers. Cylindric samples of only a few millimeters in height and in diameter were tested and led to a laser emission around 1064 nm, characterized by a very low

  1. Microstructure, mechanical and bio-corrosion properties of Mn-doped Mg–Zn–Ca bulk metallic glass composites

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jingfeng, E-mail: jfwang@cqu.edu.cn [National Engineering Research Center for Magnesium Alloys, College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Huang, Song; Li, Yang; Wei, Yiyun [National Engineering Research Center for Magnesium Alloys, College of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China); Xi, Xingfeng; Cai, Kaiyong [College of Bioengineering, Chongqing University, Chongqing 400044 (China)

    2013-10-15

    The effects of Mn substitution for Mg on the microstructure, mechanical properties, and corrosion behavior of Mg{sub 69−x}Zn{sub 27}Ca{sub 4}Mn{sub x} (x = 0, 0.5 and 1 at.%) alloys were investigated using X-ray diffraction, compressive tests, electrochemical treatments, and immersion tests, respectively. Microstructural observations showed that the Mg{sub 69}Zn{sub 27}Ca{sub 4} alloy was mainly amorphous. The addition of Mn decreases the glass-forming ability, which results in a decreased strength from 545 MPa to 364 MPa. However, this strength is still suitable for implant application. Polarization and immersion tests in the simulated body fluid at 37 °C revealed that the Mn-doped Mg–Zn–Ca alloys have significantly higher corrosion resistance than traditional ZK60 and pure Mg alloys. Cytotoxicity test showed that cell viabilities of osteoblasts cultured with Mn-doped Mg–Zn–Ca alloys extracts were higher than that of pure Mg. Mg{sub 68.5}Zn{sub 27}Ca{sub 4}Mn{sub 0.5} exhibits the highest bio-corrosion resistance, biocompatibility and has desirable mechanical properties, which could suggest to be used as biomedical materials in the future. - Highlights: • Novel Mn-doped Mg–Zn–Ca bulk metallic glass composites were made by copper mold cast. • The strength of the Mn-doped Mg–Zn–Ca is suitable for implant application. • The Mn-doped Mg–Zn–Ca alloys have significantly high bio-corrosion resistance. • The Mn-doped Mg–Zn–Ca alloys show better cell viabilities than that of pure Mg.

  2. Method for forming silicon on a glass substrate

    Science.gov (United States)

    McCarthy, A.M.

    1995-03-07

    A method by which single-crystal silicon microelectronics may be fabricated on glass substrates at unconventionally low temperatures. This is achieved by fabricating a thin film of silicon on glass and subsequently forming the doped components by a short wavelength (excimer) laser doping procedure and conventional patterning techniques. This method may include introducing a heavily boron doped etch stop layer on a silicon wafer using an excimer laser, which permits good control of the etch stop layer removal process. This method additionally includes dramatically reducing the remaining surface roughness of the silicon thin films after etching in the fabrication of silicon on insulator wafers by scanning an excimer laser across the surface of the silicon thin film causing surface melting, whereby the surface tension of the melt causes smoothing of the surface during recrystallization. Applications for this method include those requiring a transparent or insulating substrate, such as display manufacturing. Other applications include sensors, actuators, optoelectronics, radiation hard and high temperature electronics. 15 figs.

  3. Influence of preparation pathway on the glass forming ability

    DEFF Research Database (Denmark)

    Blaabjerg, Lasse Ingerslev; Lindenberg, Eleanor; Rades, Thomas

    2017-01-01

    The glass forming ability (GFA), i.e. the ease of amorphization of drugs, is mostly investigated using the critical cooling rate upon melt quenching to generate an amorphous product via the thermodynamic pathway. However, amorphous materials can also be prepared via the kinetic pathway by milling...... cooling rate will also have a low minimal milling time and is thus a good glass former........ In this case, the time required to generate an amorphous product is called the minimal milling time. This study investigates the correlation of the GFA between these two pathways. Eighteen compounds were chosen and their GFA was investigated by determining the critical cooling rate and the minimal milling time....... It was observed that drugs, which turned amorphous upon cooling from the melt at slow cooling rates also had a low minimal milling time and vice versa. It was found that the GFA of the studied set of drugs was inherent and independent of the preparation method. It can be concluded that a drug with low critical...

  4. Laboratory Testing of Bulk Vitrified Low-Activity Waste Forms to Support the 2005 Integrated Disposal Facility Performance Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Eric M.; McGrail, B. Peter; Bagaasen, Larry M.; Rodriguez, Elsa A.; Wellman, Dawn M.; Geiszler, Keith N.; Baum, Steven R.; Reed, Lunde R.; Crum, Jarrod V.; Schaef, Herbert T.

    2006-06-30

    The purpose of this report is to document the results from laboratory testing of the bulk vitri-fied (BV) waste form that was conducted in support of the 2005 integrated disposal facility (IDF) performance assessment (PA). Laboratory testing provides a majority of the key input data re-quired to assess the long-term performance of the BV waste package with the STORM code. Test data from three principal methods, as described by McGrail et al. (2000a; 2003a), are dis-cussed in this testing report including the single-pass flow-through test (SPFT) and product con-sistency test (PCT). Each of these test methods focuses on different aspects of the glass corrosion process. See McGrail et al. (2000a; 2003a) for additional details regarding these test methods and their use in evaluating long-term glass performance. In addition to evaluating the long-term glass performance, this report discusses the results and methods used to provided a recommended best estimate of the soluble fraction of 99Tc that can be leached from the engineer-ing-scale BV waste package. These laboratory tests are part of a continuum of testing that is aimed at improving the performance of the BV waste package.

  5. Laboratory Testing of Bulk Vitrified Low-Activity Waste Forms to Support the 2005 Integrated Disposal Facility Performance Assessment

    Energy Technology Data Exchange (ETDEWEB)

    Pierce, Eric M.; McGrail, B. Peter; Bagaasen, Larry M.; Rodriguez, Elsa A.; Wellman, Dawn M.; Geiszler, Keith N.; Baum, Steven R.; Reed, Lunde R.; Crum, Jarrod V.; Schaef, Herbert T.

    2005-03-31

    The purpose of this report is to document the results from laboratory testing of the bulk vitri-fied (BV) waste form that was conducted in support of the 2005 integrated disposal facility (IDF) performance assessment (PA). Laboratory testing provides a majority of the key input data re-quired to assess the long-term performance of the BV waste package with the STORM code. Test data from three principal methods, as described by McGrail et al. (2000a; 2003a), are dis-cussed in this testing report including the single-pass flow-through test (SPFT) and product con-sistency test (PCT). Each of these test methods focuses on different aspects of the glass corrosion process. See McGrail et al. (2000a; 2003a) for additional details regarding these test methods and their use in evaluating long-term glass performance. In addition to evaluating the long-term glass performance, this report discusses the results and methods used to provided a recommended best estimate of the soluble fraction of 99Tc that can be leached from the engineer-ing-scale BV waste package. These laboratory tests are part of a continuum of testing that is aimed at improving the performance of the BV waste package.

  6. Friction Stir Welding of Zr_(55)Al_(10)Ni_5Cu_(30) Bulk Metallic Glass to Crystalline Aluminum

    Institute of Scientific and Technical Information of China (English)

    Zuoxiang Qin; Cuihong Li; Haifeng Zhang; Zhongguang Wang; Zhuangqi Hu; Zhiqiang Liu

    2009-01-01

    The Zr_(55)Al_(10)Ni_5Cu_(30) bulk metallic glass plate were successfully welded to crystalline aluminum plates by using a friction stir welding (FSW) method. The welded zone was examined. No defects, cracks or pores were observed and no other crystalline phases except for aluminum were found in the welded joint. The strength of the joint is higher than that of aluminum. The glassy phase in the stir zone keeps the amorphous state, showing a successful welding. The storage modulus softens over the glass transition. And the weldability was discussed according to this phenomena.

  7. Corrosion and oxidation properties of the refractory (Ni{sub 8}Nb{sub 5}){sub 99.8}Sb{sub 0.2} bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Lu, J; Zhang, J; Shek, C, E-mail: junxialu2@student.cityu.edu.h [Department of Physics and Materials Science, City University of Hong Kong (Hong Kong)

    2009-01-01

    Bulk metallic glass (BMG) with high corrosion resistance and high oxidation resistance was synthesized in the Ni-Nb-Sb system with the diameter of 3mm. The glass transition temperature (T{sub g}), the reduced glass transition temperature (T{sub rg}=T{sub g}/T{sub l}) and supercooled liquid span (DELTAT{sub x}) are 873K, 0.59 and 54K, respectively. These thermal data indicate that this kind of Ni-based glass can maintain its stable amorphous state and resist crystallization in a rather wide temperature region. Electrochemical measurements indicate that it shows high corrosion resistance in aggressive hydrochloric acid solution with 1N and 6N concentration, respectively, at room temperature. Surface forms stable passive film and presents low current density. The oxidation kinetics follows a parabolic rate law at 853K. The x-ray diffraction pattern showed that the oxide layer is composed of Nb{sub 2}O{sub 5}, Ni{sub 3}Nb and metallic Ni. The oxide surface morphologies showed that a layer of compact oxide film formed, which shows no obvious grain boundary.

  8. Corrosion and oxidation properties of the refractory (Ni8Nb5)99.8Sb0.2 bulk metallic glass

    Science.gov (United States)

    Lu, J.; Zhang, J.; Shek, C.

    2009-01-01

    Bulk metallic glass (BMG) with high corrosion resistance and high oxidation resistance was synthesized in the Ni-Nb-Sb system with the diameter of 3mm. The glass transition temperature (Tg), the reduced glass transition temperature (Trg=Tg/Tl) and supercooled liquid span (ΔTx) are 873K, 0.59 and 54K, respectively. These thermal data indicate that this kind of Ni-based glass can maintain its stable amorphous state and resist crystallization in a rather wide temperature region. Electrochemical measurements indicate that it shows high corrosion resistance in aggressive hydrochloric acid solution with 1N and 6N concentration, respectively, at room temperature. Surface forms stable passive film and presents low current density. The oxidation kinetics follows a parabolic rate law at 853K. The x-ray diffraction pattern showed that the oxide layer is composed of Nb2O5, Ni3Nb and metallic Ni. The oxide surface morphologies showed that a layer of compact oxide film formed, which shows no obvious grain boundary.

  9. Single agglutinates: A comparative study of compositions of agglutinitic glass, whole-grain, bulk soil, and FMR

    Science.gov (United States)

    Basu, A.; Robinson, R.; Mckay, D. S.; Blanchard, D. P.; Morris, R. V.; Wentworth, Susan J.

    1994-01-01

    Previous workers on single agglutinates have variously interpreted the composition of agglutinitic glass to represent impact melts of (1) bulk soil, (2) mixed components in finer sizes, and (3) microtargets. Separately, Papike has argued in favor of fusion of the finest fraction of bulk soils. Thirty-four single agglutinates were hand-picked from the mature Apollo 16 soil 61181 (I(sub s)/FeO = 82) and the FMR and chemical composition (INAA for Fe, Sc, Sm, Co, Ni, and Cr) of each agglutinate particle were measured. Thirteen of these single agglutinates were selected for electron beam microanalysis and imaging. Less than 1 micron spots were analyzed (for Na, Mg, Al, Si, P, S, K, Ca, Ti, Cr, Mn, Fe, Ni, and Ba) on pure glassy areas (approximately ten in each particle) selected on the basis of optical and BSE images (avoiding all clasts and inclusions) with an electron microprobe to obtain average glass compositions of each single agglutinate.

  10. Composition and size dependent brittle-to-malleable transitions of Mg-based bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Yin, Jian, E-mail: yinjiandonic@yahoo.com; Ma, Xiujun; Zhou, Zhijian

    2014-05-01

    Mg-based bulk metallic glasses (BMGs) were often treated as brittle materials. However, some Mg-based BMGs were recently reported to show malleability. In order to identify the reasons for the achievement of the brittle-to-malleable transitions in the Mg-based BMGs, we systematically investigated the mechanical properties of four Mg-based BMGs (Mg{sub 65}Cu{sub 25}Gd{sub 10}, Mg{sub 65}Cu{sub 20}Ni{sub 5}Gd{sub 10}, Mg{sub 75}Ni{sub 15}Gd{sub 10}, and Mg{sub 75}Ni{sub 15}Gd{sub 5}Nd{sub 5} BMGs) using the uniaxial compression tests on the samples with sizes of ∅1×2 mm{sup 2} and ∅2×4 mm{sup 2}. The corresponding fracture morphology was observed by scanning electron microscopy (SEM). These Mg-based BMGs displayed the composition or size dependent brittle-to-malleable transitions, accompanied by the fracture mode transition from the cleavage fracture to the shear fracture. It appeared that the Mg-based BMGs were sensitive to cleavage cracks upon loading. The brittle-to-malleable transitions of the Mg-based BMGs were related to not only the stability of shear banding but also the nucleation and propagation of cleavage cracks. It was demonstrated that the suppression of the nucleation and propagation of cleavage cracks could favor the transition from the cleavage fracture to the shear fracture and encourage the brittle-to-malleable transition for the Mg-based BMGs. The underlying mechanism for the brittle-to-malleable transitions of the Mg-based BMGs was discussed with respect to both the composition and size effects.

  11. In vivo evaluation of Zr-based bulk metallic glass alloy intramedullary nails in rat femora.

    Science.gov (United States)

    Imai, Kazuhiro; Hiromoto, Sachiko

    2014-03-01

    Zr-based bulk metallic glasses (BMG) show high corrosion resistance in vitro and higher strength and lower Young's modulus than crystalline alloys with the similar composition. This study aimed to perform an in vivo evaluation of Zr65Al7.5Ni10Cu17.5 BMG. Osteotomy of the femur was done in rats and stabilized with intramedullary nails made of Zr65Al7.5Ni10Cu17.5 BMG, Ti-6Al-4V alloy, or 316L stainless steel. Systemic and local effects of each type of nail were evaluated by measuring the levels of Cu and Ni in the blood and the surrounding soft tissue. Changes of the surface of each nail were examined by scanning electron microscopy (SEM). Healing of the osteotomy was evaluated by peripheral quantitative computed tomography and mechanical testing. No increase of Cu and Ni levels was recognized. Surface of the BMG showed no noticeable change, while Ti-6Al-4V alloy showed Ca and P deposition and 316L stainless steel showed surface irregularities and pitting by SEM observation. The stress strain index, maximum torque, torsional stiffness, and energy absorption values were larger for the BMG than those for Ti-6Al-4V alloy, although there was no significant difference. The Zr-based BMG can promote osteotomy healing as fast as Ti-6Al-4V alloy, with the possible advantage of the Zr-based BMG that bone bonding is less likely, allowing easier nail removal compared with Ti-6Al-4V alloy. The Zr-based BMG is promising for the use in osteosynthetic devices that are eventually removed.

  12. Magnetic properties and power losses in Fe-Co-based bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Piccin, R. [Dip. Chim. IFM and NIS, Universita di Torino, Via P. Giuria 9, Torino 10125 (Italy)], E-mail: rafael.piccin@unito.it; Tiberto, P. [Electromagnetism Division, INRIM, Strade delle Cacce 91, Torino 10135 (Italy); Chiriac, H. [National Institute of Research and Development for Technical Physics, 47 Mangeron Blvd., Iasi 700050 (Romania); Baricco, M. [Dip. Chim. IFM and NIS, Universita di Torino, Via P. Giuria 9, Torino 10125 (Italy)

    2008-10-15

    Magnetic properties of Fe-Co-based bulk metallic glasses have been experimentally investigated. Samples were prepared by water-cooled Cu-mold injection casting technique. The samples have cylindrical shapes with 0.8 mm diameter and 30 mm length. Amorphous structures were confirmed by the presence of a main halo in X-ray diffraction patterns and by the detection of crystallization signal around 650 deg. C using differential scanning calorimetry. Owing to their amorphous structure, these materials present good soft magnetic properties with coercivity below 100 A/m and magnetic induction around 1.0 T in quasi-static conditions. Hysteresis loops were measured using a digital wattmeter with controlled induction waveform. Power losses were analyzed for the following compositions: [(Fe{sub 1-x}Co{sub x}){sub 75}B{sub 20}Si{sub 5}]{sub 93}Nb{sub 4}Y{sub 3} (x=0, 0.2, 0.4, 0.5 and 0.6) over a range of frequencies from 1 to 400 Hz at selected fixed peak inductions. Co addition has shown to improve the soft magnetic properties when x=0.2, 0.4 and 0.5, decreasing coercive fields and power losses, while the magnetic induction is slightly increased (except for x=0.5). Further Co addition (x=0.6) is detrimental for the soft magnetic properties due to the presence of crystalline {alpha}-Fe-(Co) and boride phases. The frequency dependence of power losses was described using a separation theory. It has been observed that an f{sup 1/2} rule is in good agreement with the experimental data.

  13. Glass-forming Ability and Chemical Stability of Mag-neto-optical Glass Heavily Doped with Rare Earth Oxide

    Institute of Scientific and Technical Information of China (English)

    YIN Hairong; ZHANG Chunxiang; LIU Liying; CHEN Guoping; TANG Baojun

    2009-01-01

    The glass-forming region of B_2O_3-Al_2O_3-SiO_2(BAS)glass heavily doped with rare earth oxides was investigated by an effective method,and the chemical stability was investigated by powder method.Influences of rare earth oxides on the glass-forming ability and the chemical stability of the BAS glass were also discussed.The experimental results show that the BAS glass-forming re-gion expands firstly with the increase of the Tb_2O_3 content up to 30mol%and then shrinks.The acid-resistant capacity of the BAS glass doped with rare earth oxides is the lowest,the water-resistant capacity is secondary,and the alkali-resistant capacity is the best.Besides,the glass chemical stability can be improved by doping appropriate amount of rare earth oxides.Moreover,the stronger the ionic polarization ability of the rare earth ions is,the better the chemical stability of the BAS glass will be.

  14. Photochromic glass thin film formed by the sol-gel coating method

    Science.gov (United States)

    Nakazumi, Hiroyuki; Nagashiro, Rie; Matsumoto, Shinya; Isagawa, Kakuzoh

    1994-10-01

    The photochromic gel thin films using 1'-butyl-3',3'-dimethyl-6-nitro-spiro[2H-1- benzopyran-2,2'-indoline] (1) and 1'-butyl-spiro[2H-indole-2,3'- [3H]naphtho[2,1-b][1,4]oxazine] (2) dispersed in sol in the sol-gel processing were prepared and photochromic behaviors of these films were investigated. A good transparent coating layer on glass surface was formed in the range of ca. 6 - 10 wt% of 1 or 2 to alkoxysilane, and was colored by UV irradiation. The absorption band formed by UV-irradiation disappeared by thermal decay and also by Vis irradiation for 1. The thermal fading of the colored form to the spiro form 1 or 2 is dependent on a matrix of the gels, the colored forms in the film starting from methyltriethoxysilane (MTES), which is expected to include larger pores than in the film starting from tetraethoxysilane (TEOS) or silane oligomer, show faster thermal fading which roughly follows the first order kinetics. The colored form in the gel is stabilized, compared with that in solution or bulk gel, and it is suggested that there are some kinds of colored species in thin gel films containing spiropyran 1, which may be some aggregates, whereas only a colored species from spironaphthooxazine 2 is suggested. Photochromic behavior of 2 in sol was also examined.

  15. Thermal stability and magnetic properties of Fe–Co–M–Zr–Nb–Ge–B (M=Mo, Cr bulk metallic glasses

    Directory of Open Access Journals (Sweden)

    Min Xu

    2014-04-01

    Full Text Available Fe62Co8−xMxZr6Nb4Ge1B19 (M=Mo, Cr bulk metallic glasses were synthesized in the diameter range up to 2 mm by copper mold casting, which exhibit high thermal stability and large glass-forming ability. The super-cooled liquid region diminishes by the dissolution of Mo. The addition of 2 at% Cr leads to the broading of the liquid region remarkably, resulting in the improvement of thermal stability. The crystallization takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such as α-Fe, Fe2Zr and ZrB2. The Fe-based alloys show soft ferromagnetic properties. The saturation magnetization (σs decreases with increasing Mo or Cr content while the saturated magnetostriction increases with raising Mo or Cr content. There is no evident change in the σs and coercive force (Hc with annealing temperature below the crystallization temperature, which suggests a more relaxed atomic configuration the glasses have. The crystallization causes a substantial enhancement in both σs and Hc. Each soft magnetic property of the glasses containing Cr with higher thermal stability is superior to that of the alloys containing Mo.

  16. Thermal stability and magnetic properties of Fe-Co-M-Zr-Nb-Ge-B (M ¼ Mo, Cr) bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    Min Xu; Qunjiao Wang

    2014-01-01

    Fe62Co8-xMxZr6Nb4Ge1B19 (M=Mo, Cr) bulk metallic glasses were synthesized in the diameter range up to 2 mm by copper mold casting, which exhibit high thermal stability and large glass-forming ability. The super-cooled liquid region diminishes by the dissolution of Mo. The addition of 2 at%Cr leads to the broading of the liquid region remarkably, resulting in the improvement of thermal stability. The crystallization takes place through a single exothermic reaction, accompanying the precipitation of more than three kinds of crystallized phases such asα-Fe, Fe2Zr and ZrB2. The Fe-based alloys show soft ferromagnetic properties. The saturation magnetization (ss) decreases with increasing Mo or Cr content while the saturated magnetostriction increases with raising Mo or Cr content. There is no evident change in the ss and coercive force (Hc) with annealing temperature below the crystallization temperature, which suggests a more relaxed atomic configuration the glasses have. The crystallization causes a substantial enhancement in both ss and Hc. Each soft magnetic property of the glasses containing Cr with higher thermal stability is superior to that of the alloys containing Mo.

  17. Investigation of preparation methods on surface/bulk structural relaxation and glass fragility of amorphous solid dispersions.

    Science.gov (United States)

    Ke, Peng; Hasegawa, Susumu; Al-Obaidi, Hisham; Buckton, Graham

    2012-01-17

    The objective of this study was to investigate the effect of preparation methods on the surface/bulk molecular mobility and glass fragility of solid dispersions. Solid dispersions containing indomethacin and PVP K30 were chosen as the model system. An inverse gas chromatography method was used to determine the surface structural relaxation of the solid dispersions and these data were compared to those for bulk relaxation obtained by DSC. The values of τ(β) for the surface relaxation were 4.6, 7.1 and 1.8h for melt quenched, ball milled and spray dried solid dispersions respectively, compared to 15.6, 7.9 and 9.8h of the bulk. In all systems, the surface had higher molecular mobility than the bulk. The glass fragility of the solid dispersions was also influenced by the preparation methods with the most fragile system showing the best stability. The zero mobility temperature (T(0)) was used to correlate with the physical stability of the solid dispersions. Despite having similar T(g) (65°C), the T(0) of the melt quenched, ball milled and spray dried samples were 21.6, -4.2 and 16.7°C respectively which correlated well with their physical stability results. Therefore, T(0) appears to be a better indicator than T(g) for predicting stability of amorphous materials.

  18. Adaptive finite element-element-free Galerkin coupling method for bulk metal forming processes

    Institute of Scientific and Technical Information of China (English)

    Lei-chao LIU; Xiang-huai DONG; Cong-xin LI

    2009-01-01

    An adaptive finite element-element-free Galerkin (FE-EFG) coupling method is proposed and developed for the numerical simulation of bulk metal forming processes. This approach is able to adaptively convert distorted FE elements to EFG domain in analysis. A new scheme to implement adaptive conversion and coupling is presented. The coupling method takes both advantages of finite element method (FEM) and meshless methods. It is capable of handling large deformations with no need of remeshing procedures, while it is computationally more efficient than those full meshless methods. The effectiveness of the proposed method is demonstrated with the numerical simulations of the bulk metal forming processes including forging and extrusion.

  19. Effect of Heating Rate on Glass Foaming: Transition to Bulk Foam

    Energy Technology Data Exchange (ETDEWEB)

    Hrma, Pavel R.

    2009-02-15

    Foaming of glass is an undesirable side effect of glass fining. According to a recent experimental study, the gas-phase volume in the melt heated at a constant rate dramatically increased with an increased rate of heating. This observation indicates that an increased rate of heating (a natural consequence of the increased processing rate experienced as a result of transition to oxy-fuel firing) may exert a substantial influence on glass foaming in advanced glass-melting furnaces. This paper attributes this effect to the change of mode of foam formation in response to an increased rate of heating.

  20. SET and RESET states of As2Se3 doped GeTe4 bulk glasses probed by Raman spectroscopy

    Science.gov (United States)

    Pumlianmunga, Ramesh, K.

    2016-12-01

    Te based chalcogenide glasses are being explored for non-volatile memory applications. We report the electrical switching studies on bulk Ge0.20Te0.80 glass alloyed with As0.40Se0.60 in different proportions. The addition of As0.40Se0.60 increases the electrical resistivity and the threshold voltage of (As0.4Se0.6)x(Ge0.2Te0.8)1-x glasses in the composition range 0 ≤ x ≤ 0.40. Glasses in the range 0 ≤ x ≤ 0.10 are found to exhibit memory switching, whereas glasses with x ≥ 0.15 exhibit threshold switching. The memory (SET) state can be brought back to RESET state by passing a current of 3-5 mA. Particularly, the glass with x = 0.10 is identified to be very stable, and it can be cycled between the SET and RESET state consistently with 3 mA current. The Raman spectra of SET and RESET states indicate that the SET sample has GeTe and Te crystalline units while the structure of RESET state is analogous to the as-quenched glass. Interestingly, the variation in the local structure is minimal for SET and RESET states for x = 0.10. And also the resistance of the SET state is relatively high. So they can be set to RESET state with less current and can be explored for low power phase change memory applications.

  1. Simulation of cooling and solidification of three-dimensional bulk borosilicate glass: effect of structural relaxations

    Science.gov (United States)

    Barth, N.; George, D.; Ahzi, S.; Rémond, Y.; Joulaee, N.; Khaleel, M. A.; Bouyer, F.

    2014-02-01

    The modeling of the viscoelastic stress evolution and specific volume relaxation of a bulky glass cast is presented in this article and is applied to the experimental cooling process of an inactive nuclear waste vitrification process. The concerned borosilicate glass is solidified and cooled down to ambient temperature in a stainless steel canister, and the thermomechanical response of the package is simulated. There exists a deviant compression of the liquid core due to the large glass package compared to standard tempered glass plates. The stress load development of the glass cast is finally studied for different thermal load scenarios, where the cooling process parameters or the final cooldown rates were changed, and we found a great influence of the studied cooldown rates on the maximum stress build-up at ambient temperature.

  2. Towards Mass Production by High Performance Transfer Press in Micro Bulk Forming

    DEFF Research Database (Denmark)

    Mahshid, Rasoul; Hansen, Hans Nørgaard; Arentoft, Mogens

    2014-01-01

    cold bulk forming. A methodology for selection of linear motors on the bases of the process parameters was obtained. In order to examine the effectiveness of the machine, specific geometry was investigated for production. Kinematic parameters were found for a production rate of 200 strokes per minute...

  3. The effects of bulking, viscous and gel-forming dietary fibres on satiation

    NARCIS (Netherlands)

    Wanders, A.J.; Jonathan, M.C.; Borne, van den J.J.G.C.; Mars, M.; Schols, H.A.; Feskens, E.J.M.; Graaf, de C.

    2013-01-01

    The objective was to determine the effects of dietary fibre with bulking, viscous and gel-forming properties on satiation, and to identify the underlying mechanisms. We conducted a randomised crossover study with 121 men and women. Subjects were healthy, non-restrained eaters, aged 18–50 years and w

  4. VALIDATED SPECTROPHOTMETRIC METHOD FOR THE DETERMINATION OF SALBUTAMOL SULPHATE IN BULK AND PHARMACEUTICAL DOSAGE FORMS

    Directory of Open Access Journals (Sweden)

    Eswarudu.M.M

    2012-04-01

    Full Text Available A new, simple, accurate and sensitive spectrophotometric method has been developed for the estimation of Salbutamol sulphate in bulk and in pharmaceutical formulations. Salbutamol sulphate shows ʎ max at 292 nm. The drug follows the beer’s lambert’s law in the concentration range of 20-100µ ml. the method was validated by following the analytical performance parameters as suggested by the international conference on harmonization which included accuracy, precision, linearity. All validation parameters were with in the acceptable range. The developed method was successfully applied to estimate the amount of Salbutamol sulphate in bulk and pharmaceutical dosage forms.

  5. Spinel dissolution via addition of glass forming chemicals. Results of preliminary experiments

    Energy Technology Data Exchange (ETDEWEB)

    Fox, K. M. [Savannah River Site (SRS), Aiken, SC (United States); Johnson, F. C. [Savannah River Site (SRS), Aiken, SC (United States)

    2015-11-01

    Increased loading of high level waste in glass can lead to crystallization within the glass. Some crystalline species, such as spinel, have no practical impact on the chemical durability of the glass, and therefore may be acceptable from both a processing and a product performance standpoint. In order to operate a melter with a controlled amount of crystallization, options must be developed for remediating an unacceptable accumulation of crystals. This report describes preliminary experiments designed to evaluate the ability to dissolve spinel crystals in simulated waste glass melts via the addition of glass forming chemicals (GFCs).

  6. Non-equilibrium dynamics of glass-forming liquid mixtures.

    Science.gov (United States)

    Sánchez-Díaz, Luis Enrique; Lázaro-Lázaro, Edilio; Olais-Govea, José Manuel; Medina-Noyola, Magdaleno

    2014-06-21

    The non-equilibrium self-consistent generalized Langevin equation theory of irreversible processes in glass-forming liquids [P. Ramírez-González and M. Medina-Noyola, Phys. Rev. E 82, 061503 (2010)] is extended here to multi-component systems. The resulting theory describes the statistical properties of the instantaneous local particle concentration profiles nα(r, t) of species α in terms of the coupled time-evolution equations for the mean value n̄α(r, t) and for the covariance σ(αβ)(r, r'; t) ≡ δn(α)(r, t)δn(β)(r', t) of the fluctuations δn(α)(r, t) = n(α)(r, t) - n̄α(r, t). As in the monocomponent case, these two coarse-grained equations involve a local mobility function bα(r, t) for each species, written in terms of the memory function of the two-time correlation function C(αβ)(r, r'; t, t') ≡ δn(α)(r, t)δn(β)(r', t'). If the system is constrained to remain spatially uniform and subjected to a non-equilibrium preparation protocol described by a given temperature and composition change program T(t) and n̄α(r, t), these equations predict the irreversible structural relaxation of the partial static structure factors Sαβ(k; t) and of the (collective and self) intermediate scattering functions Fαβ(k, τ; t) and F(αβ)(S)(k, τ; t). We illustrate the applicability of the resulting theory with two examples involving simple model mixtures subjected to an instantaneous temperature quench: an electroneutral binary mixture of equally sized and oppositely charged hard-spheres, and a binary mixture of soft-spheres of moderate size-asymmetry.

  7. Rapid Finite Element Analysis of Bulk Metal Forming Process Based on Deformation Theory

    Institute of Scientific and Technical Information of China (English)

    WANG Peng; DONG Xiang-huai; FU Li-jun

    2009-01-01

    The one-step finite element method (FEM), based on plastic deformation theory, has been widely used to simulate sheet metal forming processes, but its application in bulk metal forming simulation has been seldom investigated, because of the complexity involved. Thus, a bulk metal forming process was analyzed using a rapid FEM based on deformation theory. The material was assumed to be rigid-plastic and strain-hardened. The constitutive relationship between stress and total strain was adopted, whereas the incompressible condition was enforced by penalty function. The geometrical non-linearity in large plastic deformation was taken into consideration. Furthermore, the force boundary condition was treated by a simplified equivalent approach, considering the contact history. Based on constraint variational principle, the deformation FEM was proposed. The one-step forward simulation of axisymmetric upsetting process was performed using this method. The results were compared with those obtained by the traditional incremental FEM to verify the feasibility of the proposed method.

  8. Crystallization in Zr60Al15Ni25 bulk metallic glass subjected to rolling at room temperature

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The microstructure evolution of Zr60Al15Ni25 bulk metallic glass during rolling at room temperature is investigated by differential scanning calorimetry(DSC),high-resolution transmission electron microscopy(HRTEM) and selected area electronic diffraction(SAED).The HRTEM images show that shear bands are produced in the rolled specimens,indicating the essence of inhomogeneous deformation due to rolling,and that there exist nanocrystals with size of about 5-10 nm in the transition regions between the shear bands and the undeformed matrix in the rolled specimens with deformation degrees of 80% and 95%.Based on the polyhedral structure model and the shear transformation zone(STZ) theory,the influence of viscous flow,free volume,viscosity and the stress situation on the crystallization behaviors in the metallic glass during rolling is discussed.

  9. Glass Ceramic Waste Forms for Combined CS+LN+TM Fission Products Waste Streams

    Energy Technology Data Exchange (ETDEWEB)

    Crum, Jarrod V.; Turo, Laura A.; Riley, Brian J.; Tang, Ming; Kossoy, Anna; Sickafus, Kurt E.

    2010-09-23

    In this study, glass ceramics were explored as an alternative waste form for glass, the current baseline, to be used for immobilizing alkaline/alkaline earth + lanthanide (CS+LN) or CS+LN+transition metal (TM) fission-product waste streams generated by a uranium extraction (UREX+) aqueous separations type process. Results from past work on a glass waste form for the combined CS+LN waste streams showed that as waste loading increased, large fractions of crystalline phases precipitated upon slow cooling.[1] The crystalline phases had no noticeable impact on the waste form performance by the 7-day product consistency test (PCT). These results point towards the development of a glass ceramic waste form for treating CS+LN or CS+LN+TM combined waste streams. Three main benefits for exploring glass ceramics are: (1) Glass ceramics offer increased solubility of troublesome components in crystalline phases as compared to glass, leading to increased waste loading; (2) The crystalline network formed in the glass ceramic results in higher heat tolerance than glass; and (3) These glass ceramics are designed to be processed by the same melter technology as the current baseline glass waste form. It will only require adding controlled canister cooling for crystallization into a glass ceramic waste form. Highly annealed waste form (essentially crack free) with up to 50X lower surface area than a typical High-Level Waste (HLW) glass canister. Lower surface area translates directly into increased durability. This was the first full year of exploring glass ceramics for the Option 1 and 2 combined waste stream options. This work has shown that dramatic increases in waste loading are achievable by designing a glass ceramic waste form as an alternative to glass. Table S1 shows the upper limits for heat, waste loading (based on solubility), and the decay time needed before treatment can occur for glass and glass ceramic waste forms. The improvements are significant for both combined waste

  10. Effect of annealing and cobalt content on relaxation and crystallization behavior of zirconium based bulk metallic glasses

    Science.gov (United States)

    Dong, Yue; Wunderlich, Rainer; Fecht, Hans-Jörg

    2017-08-01

    The effects of annealing and cobalt content on relaxation and the crystallization process of Zr64Ni10Al7Cu19 bulk metallic glasses were investigated. β-relaxation occurs during annealing, leading to increased endotherm before crystallization. α-relaxation during high temperature annealing (higher than Tg) affects the crystallization process. The introduction of cobalt leads to an inhomogeneous amorphous structure and two-step crystallization due to the positive mixing enthalpy between cobalt and copper. Non-affine thermal strain arising from low temperature annealing of heterogeneous structure leads to a reduced endotherm phenomenon during relaxation on the DSC curves and a reduction in hardness.

  11. The Effect of Ag Addition on the Enhancement of the Thermal and Mechanical Properties of CuZrAl Bulk Metallic Glasses

    Directory of Open Access Journals (Sweden)

    Tsan-Man Chung

    2016-09-01

    Full Text Available In this study, the thermal and mechanical properties of Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6 bulk metallic glasses (BMGs are investigated by using an X-ray diffractometer (XRD, a differential scanning calorimeter (DSC, differential thermal analysis (DTA, a Vickers hardness tester, a material test system (MTS, scanning electron microscopy (SEM, and transmission electron microscopy (TEM. Cu50−xZr43Al7Agx (x = 0, 3, 4, 5, 6 BMGs were made by arc-melting and an injection casting process. The results revealed that the glass transition temperature (Tg and the crystallization temperature (Tx of CuZrAl alloy decreased with the Ag addition. Hence, the supercooled liquid region and γ of Cu45Zr43Al7Ag5 alloy increased to 76 K and 0.42, respectively. The thermal stability and glass forming ability of CuZrAlAg BMG alloys were enhanced by the microalloyed Ag content. The room temperature compressive fracture strength and strain measured of Cu47Zr43Al7Ag3 were about 2200 MPa and 2.1%, respectively. The distribution of vein patterns and the formation of nanocrystalline phases on the fracture surface of Cu47Zr43Al7Ag3 alloy can be observed by SEM and TEM to be significant, indicating a typical ductile fracture behavior and an improved plasticity of alloys with the addition of microalloyed Ag from 0 to 6 atom %.

  12. Chalcogenide Glass for Passive Infrared Applications

    Institute of Scientific and Technical Information of China (English)

    Xianghua Zhang; Hongli Ma; Jacques Lucas

    2003-01-01

    Chalcogenide glass fibers have been successfully used for remote spectroscopy, temperature sensing and CO2 laser power delivery. In bulk form, chalcogenide glass is the most promising candidate for replacing the expensive germanium lenses for thermal imaging.

  13. Theory and simulations of quantum glass forming liquids.

    Science.gov (United States)

    Markland, Thomas E; Morrone, Joseph A; Miyazaki, Kunimasa; Berne, B J; Reichman, David R; Rabani, Eran

    2012-02-21

    A comprehensive microscopic dynamical theory is presented for the description of quantum fluids as they transform into glasses. The theory is based on a quantum extension of mode-coupling theory. Novel effects are predicted, such as reentrant behavior of dynamical relaxation times. These predictions are supported by path integral ring polymer molecular dynamics simulations. The simulations provide detailed insight into the factors that govern slow dynamics in glassy quantum fluids. Connection to other recent work on both quantum glasses as well as quantum optimization problems is presented.

  14. Investigation of the microcrack evolution in a Ti-based bulk metallic glass matrix composite

    Institute of Scientific and Technical Information of China (English)

    Yongsheng Wang; Zhenxi Guo; Rui Ma; Guojian Hao; Yong Zhang; Junpin Lin; Manling Sui

    2014-01-01

    The initiation and evolution behavior of the shear-bands and microcracks in a Ti-based metallic-glass-matrix composite (MGMC) were investigated by using an in-situ tensile test under transmission electron microscopy (TEM). It was found that the plastic deformation of the Ti-based MGMC related with the generation of the plastic deformation zone in crystalline and shear deformation zone in glass phase near the crack tip. The dendrites can suppress the propagation of the shear band effectively. Before the rapid propagation of cracks, the extending of plastic deformation zone and shear deformation zone ahead of crack tip is the main pattern in the composite.

  15. Effect of incongruent crystallization on glass–liquid transition features of a bulk metal glass

    Energy Technology Data Exchange (ETDEWEB)

    Aji, D.P.B.; Johari, G.P., E-mail: joharig@mcmaster.ca

    2015-09-10

    Highlights: • Ce{sub 66}Al{sub 10}Cu{sub 20}Co{sub 4} glass did not crystallize during aging for nine years. • Crystallization's onset temperature was higher for the aged glass. • Incongruent melt embedding the crystals had higher viscosity and T{sub g}. • Increase in crystallization increased the T{sub g} and broadened the T{sub g}-endotherm. - Abstract: It is known that most multi-component glasses cold-crystallize incongruently on heating through the temperature range of their ultraviscous melt. If the incongruent melt's composition changes with time, its viscosity, η, and the glass–liquid transition temperature, T{sub g}, would change. Since the η, relaxation time, and expansion coefficient of a liquid in its partially crystallized mixture cannot be determined, we used scanning calorimetry to study the liquid–glass–liquid transition during thermal cycling of the incongruently crystallizing Ce{sub 66}Al{sub 10}Cu{sub 20}Co{sub 4} glass. Its T{sub g} is 358 K for 20 K/min and 354 K for 10 K/min heating rates, and its ultraviscous melt crystallized incongruently when heated beyond the hysteresis peak of its heat capacity scan. Its sample that had been aged for nine years at ambient conditions had a higher crystallization-onset temperature than an un-aged sample. Delayed enthalpy gain on heating of the aged glass is ∼1/5th of the enthalpy lost on its crystallization. Crystallization of the melt occurred on both the heating and cooling paths of a thermal cycle and T{sub g} of the un-aged glass increased as the volume fraction of the compositionally different glass, f{sub gl}, decreased. The increase was by 8 K after the 24th cycle of 20 K/min, and by 11 K after the 13th cycle of 10 K/min cooling-heating. The highest T{sub g} values reached differed by ∼1 K, which indicates that closely similar T{sub g}s may be reached if the total time period for thermal cycling (at different rates) is kept the same. As f{sub gl} approached its limiting

  16. Thermodynamics and fragility of glass-forming alloys

    Energy Technology Data Exchange (ETDEWEB)

    Battezzati, L., E-mail: livio.battezzati@unito.it [Dipartimento di Chimica e Centro NIS, Università di Torino, Via P. Giuria 7, 10125 Torino (Italy); Dalla Fontana, G. [Dipartimento di Chimica e Centro NIS, Università di Torino, Via P. Giuria 7, 10125 Torino (Italy)

    2014-02-15

    Highlights: ► Thermodynamic and dynamic properties of metallic melts compared with those of other glass formers. ► Relationships between ΔS{sub g}/ΔC{sub p,g} and relevant temperatures for the glass demonstrated. ► Correspondence with either hyperbolic or Gaussian distribution of the states in the PEL shown. ► Correlations allow estimate of unknown quantities and pinpoint peculiar behavior of liquid. -- Abstract: The existing correlation between the extensive properties, ΔH and ΔS, the enthalpy and entropy difference between liquid and crystal phases has been checked to relate metallic glasses to other classes of amorphous materials. Expressing the specific heat difference, ΔC{sub p}, of molten and crystalline metallic glass-formers as a function of temperature with different functional trends, parametric expressions of fragility are derived using relevant temperatures for alloys. It is shown that relationships between the ΔS{sub g}/ΔC{sub p,g} ratio and such temperatures are useful to estimate unknown quantities when the experimental determination of the specific heat is possible. Thermodynamic indicators of fragility are compared to the kinetic fragility obtained from viscosity data accounting for the estimated errors on parameters which are derived from extrapolations. The outcome of the analysis indicates that a relationship between thermodynamic and kinetic parameters exists. Moreover a systematic scatter for some alloys indicates a diverse behavior which can be ascribed to structure modification either in the liquid or in the solid reference state.

  17. Communication: High pressure specific heat spectroscopy reveals simple relaxation behavior of glass forming molecular liquid

    DEFF Research Database (Denmark)

    Roed, Lisa Anita; Niss, Kristine; Jakobsen, Bo

    2015-01-01

    The frequency dependent specific heat has been measured under pressure for the molecular glass forming liquid 5-polyphenyl-4-ether in the viscous regime close to the glass transition. The temperature and pressure dependences of the characteristic time scale associated with the specific heat...

  18. Effect of low dose electron beam irradiation on the alteration layer formed during nuclear glass leaching

    Science.gov (United States)

    Mougnaud, S.; Tribet, M.; Renault, J.-P.; Jollivet, P.; Panczer, G.; Charpentier, T.; Jégou, C.

    2016-12-01

    This investigation concerns borosilicate glass leaching mechanisms and the evolution of alteration layer under electron beam irradiation. A simple glass doped with rare earth elements was selected in order to access mechanistic and structural information and better evaluate the effects of irradiation. It was fully leached in initially pure water at 90 °C and at high glass surface area to solution volume ratio (S/V = 20 000 m-1) in static conditions. Under these conditions, the system quickly reaches the residual alteration rate regime. A small particle size fraction (2-5 μm) was sampled in order to obtain a fairly homogeneous altered material enabling the use of bulk characterization methods. External irradiations with 10 MeV electrons up to a dose of 10 MGy were performed either before or after leaching, to investigate respectively the effect of initial glass irradiation on its alteration behavior and the irradiation stability of the alteration layer. Glass dissolution rate was analyzed by regular leachate samplings and the alteration layer structure was characterized by Raman, luminescence (continuous or time-resolved), and 29Si MAS NMR and EPR spectroscopy. It was shown that the small initial glass evolutions under irradiation did not induce any modification of the leaching kinetic nor of the structure of the alteration layer. The alteration process seemed to "smooth over" the created defects. Otherwise, the alteration layer and initial glass appeared to have different behaviors under irradiation. No Eu3+ reduction was detected in the alteration layer after irradiation and the defect creation efficiency was much lower than for initial glass. This can possibly be explained by the protective role of pore water contained in the altered material (∼20%). Moreover, a slight depolymerization of the silicon network of the altered glass under irradiation with electrons was evidenced, whereas in the initial glass it typically repolymerizes.

  19. Microscale Mechanical Deformation Behaviors and Mechanisms in Bulk Metallic Glasses Investigated with Micropillar Compression Experiments

    Science.gov (United States)

    Ye, Jianchao

    2011-12-01

    Over the past years of my PhD study, the focused-ion-beam (FIB) based microcompression experiment has been thoroughly investigated with respect to the small-scale deformation in metallic glasses. It was then utilized to explore the elastic and plastic deformation mechanisms in metallic glasses. To this end, micropillars with varying sample sizes and aspect ratios were fabricated by the FIB technique and subsequently compressed on a modified nanoindentation system. An improved formula for the measurement of the Young's modulus was derived by adding a geometrical prefactor to the Sneddon's solution. Through the formula, geometry-independent Young's moduli were extracted from microcompression experiments, which are consistent with nanoindentation results. Furthermore, cyclic microcompression was developed, which revealed reversible inelastic deformation in the apparent elastic regime through high-frequency cyclic loading. The reversible inelastic deformation manifests as hysteric loops in cyclic microcompression and can be captured by the Kelvin-type viscoelastic model. The experimental results indicate that the free-volume zones behave essentially like supercooled liquids with an effective viscosity on the order of 1 x 108 Pas. The microscopic yield strengths were first extracted with a formula derived based on the Mohr-Coulomb law to account for the geometrical effects from the tapered micropillar and the results showed a weak size effect on the yield strengths of a variety of metallic-glass alloys, which can be attributed to Weibull statistics. The nature of the yielding phenomenon was explored with the cyclic micro-compression approach. Through cyclic microcompression of a Zr-based metallic glass, it can be demonstrated that its yielding stress increases at higher applied stress rate but its yielding strain is kept at a constant of ~ 2%. The room-temperature post-yielding deformation behavior of metallic glasses is characterized by flow serrations, which were

  20. An impedance-measurement setup optimized for measuring relaxations of glass-forming liquids.

    Science.gov (United States)

    Igarashi, Brian; Christensen, Tage; Larsen, Ebbe H; Olsen, Niels Boye; Pedersen, Ib H; Rasmussen, Torben; Dyre, Jeppe C

    2008-04-01

    An electronics system has been assembled to measure frequency-dependent response functions of glass-forming liquids in the extremely viscous state approaching the glass transition. We determine response functions such as dielectric permittivity and shear and bulk moduli by measuring electrical impedances of liquid-filled transducers, and this technique requires frequency generators capable of producing signals that are reproducible over the span of several days or even several weeks. To this end, we have constructed a frequency generator that produces low-frequency (1 mHz-100 Hz) sinusoidal signals with voltages that are reproducible within 10 ppm. Two factors that partly account for this precision are that signals originate from voltages stored in a look-up table and that only coil-less filters are used in this unit, which significantly reduces fluctuations of output caused by changes of temperatures of circuits. This generator also includes a special triggering facility that makes it possible to measure up to 512 voltages per cycle that are spaced apart at uniform phase intervals. Fourier transformations of such data yield precise determinations of complex amplitudes of voltages and currents applied to a transducer, which ultimately allows us to determine electrical impedances of transducers with a reproducibility error that is only a few parts per hundred thousand. This equipment is used in tandem with a commercial LCR meter and/or impedance analyzer that give(s) impedance measurements at higher frequencies, up to 1 MHz. The experimental setup allows measurements of the transducer impedance over nine decades of frequency within a single run.

  1. UV-SPECTROPHOTOMETRIC METHOD FOR ESTIMATION OF SECNIDAZOLE IN BULK AND TABLET DOSAGE FORM

    Directory of Open Access Journals (Sweden)

    Jinendra M. Sonpetkar et al.

    2012-02-01

    Full Text Available A simple, precise and accurate UV-Spectrophotometric method has been developed and validated for estimation of secnidazole in bulk and tablet dosage form. It shows maximum absorbance at 313 nm with methanol and water (30:70. Estimation was carried out by A(1%1cm and by comparison with standard. Calibration graph was found to be linear (r2 =0.09998 over concentration range of 1-4µg/ml. The proposed methods appear to be simple, sensitive, and reproducible when checked for parameters like accuracy, precision, limit of detection for routine determination of secnidazole in bulk as well as in tablet. The methods can be adopted in its routine analysis.

  2. On a solution to the problem of the poor cyclic fatigue resistance of bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Launey, Maximilien E.; Hofmann, Douglas C.; Johnson, William L.; Ritchie, Robert O.

    2009-01-09

    The recent development of metallic glass-matrix composites represents a particular milestone in engineering materials for structural applications owing to their remarkable combinations of strength and toughness. However, metallic glasses are highly susceptible to cyclic fatigue damage and previous attempts to solve this problem have been largely disappointing. Here we propose and demonstrate a microstructural design strategy to overcome this limitation by matching the microstructural length scales (of the second phase) to mechanical crack-length scales. Specifically, semi-solid processing is used to optimize the volume fraction, morphology, and size of second phase dendrites to confine any initial deformation (shear banding) to the glassy regions separating dendrite arms having length scales of {approx} 2 {micro}m, i.e., to less than the critical crack size for failure. Confinement of the damage to such interdendritic regions results in enhancement of fatigue lifetimes and increases the fatigue limit by an order of magnitude making these 'designed' composites as resistant to fatigue damage as high-strength steels and aluminum alloys. These design strategies can be universally applied to any other metallic glass systems.

  3. Mechanical Property and Corrosion Resistance Evaluations of Ti-6Al-7Nb Alloy Brazed with Bulk Metallic Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Miura, E. [Nagasaki University, Nagasaki, Japan; Kato, H. [Tohoku University, Japan; Ogata, Toshiaki [Nagasaki University, Nagasaki, Japan; Nishiyama, Nobuyuki [Tohoku University, Japan; Specht, Eliot D [ORNL; Shiraishi, Takanobu [ORNL; Inoue, A. [Tohoku University, Japan; Hisatsune, K. [Nagasaki University, Nagasaki, Japan

    2007-01-01

    Exploitation of metallic glass as new brazing filler for Ti-based biomedical alloy was attempted. Ti-6Al-7Nb was used as a brazed material, and candidates of bulk metallic glass brazing filler were Cu60Hf25Ti15, Mg65Cu25Gd10, Zr55Cu30Al10Ni5 and Pd40Cu30P20Ni10. Convergence infrared-ray brazing was conducted for brazing Ti-6Al-7Nb/metallic glass in Ar atmosphere. After brazing, hardness measurement, X-ray tomography, cross-sectional observation, artificial saliva immersion test and tensile test were performed to evaluate brazability, mechanical property and corrosion resistance of the obtained brazing joints. The results of brazing using these metallic glass fillers show that all the metallic glasses were brazable to Ti-6Al-7Nb except for Mg65Cu25Gd10. Mg65Cu25Gd10, Cu60Hf25Ti15 and their joints collapsed rapidly during immersion test. Zr55Cu30Al10Ni5 joint was the best in terms of degradation resistance; however, tensile strength was inferior to the conventional one. Pd40Cu30Ni10P20 filler and Zr55Cu30Al10Ni5 filler and their joints did not show any collapse or tarnish during the immersion test. Pd40Cu30Ni10P20 joint showed the excellent properties in terms of both corrosion resistance and tensile strength, which were superior to a joint brazed using Ti-15Cu-25Ni conventional filler. X-ray tomograph indicates that fracture tends to occur in the vicinity of the brazing interface after tensile test. The brazed metallic glass fillers were fully crystallized, excluding Pd40Cu30Ni10P20 filler. Pd40Cu30Ni10P20 brazed filler contained mapleleaf like primary dendrite, peritectoid and a few microns interfacial reaction layer in glassy matrix. The results indicated that Pd40Cu30Ni10P20 is promising brazing filler for dental or biomaterial devices.

  4. The effects of initial welding temperature and welding parameters on the crystallization behaviors of laser spot welded Zr-based bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Huei-Sen, E-mail: huei@mail.isu.edu.tw [Department of Materials Science and Engineering, I-Shou University, Kaohsiung County 84001, Taiwan (China); Chiou, Mau-Sheng; Chen, Hou-Guang [Department of Materials Science and Engineering, I-Shou University, Kaohsiung County 84001, Taiwan (China); Jang, Jason Shian-Ching [Department of Mechanical Engineering, National Central University, Taoyuan County 32001, Taiwan (China)

    2011-09-15

    This study investigated the effects of the initial welding temperature (IWT) and welding parameters on the crystallization behaviors of laser spot welded (Zr{sub 53}Cu{sub 30}Ni{sub 9}Al{sub 8})Si{sub 0.5} bulk metallic glass (BMG). After the welding process, the microstructure evolution, glass-forming ability (GFA) and mechanical properties of the welded samples were determined by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC) and the Vicker's micro-hardness test. The results showed that the heat-affected zone (HAZ) crystallization seemed avoidable under the room temperature welding process. However, with a combination of a lower energy input (welding Condition C) and a lower IWT (at 0 deg. C), a crystallization-free HAZ was finally obtained. Using the above welding condition into the refined heat flow equation, a critical retention time of 79 ms for the crystallization temperature interval was estimated. Moreover, as the laser welded samples came to crystallization in the HAZ, it was observed that a higher content of spherical-type crystalline precipitates tended to result in a higher value of glass transition temperature, T{sub g}. Therefore, the GFA indices, {Delta}T{sub x}, {gamma} and {gamma}{sub m}, were reduced. Furthermore, it was found that the micro-hardness value in the HAZ crystallization area was decreased due to the massive cracks formed in most parts of the crystalline precipitates. For a crystallization-free HAZ, the hardness seemed unaffected.

  5. New Zr-based glass-forming alloys containing Gd and Sm

    Directory of Open Access Journals (Sweden)

    Luis César Rodríguez Aliaga

    2012-10-01

    Full Text Available The effect of minor additions of Gd and Sm on the glass-forming ability (GFA of Cu-Zr-Al alloys is investigated here. The rationale for these additions is the fact that the atomic size distribution can increase GFA by changing the topology of the alloy as a function of cluster stability, which is tied to the electronegativity and ionic and covalent nature of alloys. Ingots with nominal compositions of Cu40Zr49Al10.5Gd0.5, Cu40Zr49Al10.5Sm0.5 and Cu39Zr50Al9Gd2 were prepared by arc-melting and rapidly quenched ribbons were produced by the melt-spinning technique. Bulk samples with a thickness of up to 10 mm were also produced by casting, using a wedge-shaped copper mold. The samples were characterized by differential scanning calorimetry, X-ray diffractometry and scanning electron microscopy. The three compositions showed a fully amorphous structure in the ribbons and a predominantly homogeneous amorphous structure with a thickness of up to 10 mm, although some gadolinium oxide crystals as well as samarium compounds were found to be scattered in the amorphous matrix in 5-mm-thick samples. The amorphous phases in the alloys showed high thermal stability with a supercooled liquid region (ΔTx of about 70 K.

  6. Microcraters formed in glass by projectiles of various densities

    Science.gov (United States)

    Vedder, J. F.; Mandeville, J.-C.

    1974-01-01

    An experiment was conducted investigating the effect of projectile density on the structure and size of craters in soda lime glass and fused quartz. The projectiles were spheres of polystyrene-divinylbenzene (PS-DVB), aluminum, and iron with velocities between 0.5 and 15 km/sec and diameters between 0.4 and 5 microns. The projectile densities spanned the range expected for primary and secondary particles of micrometer size at the lunar surface, and the velocities spanned the lower range of micrometeoroid velocities and the upper range of secondary projectile velocities. There are changes in crater morphology as the impact velocity increases, and the transitions occur at lower velocities for the projectiles of higher density. The sequence of morphological features of the craters found for PS-DVB impacting soda lime glass for increasing impact velocity, described in a previous work (Mandeville and Vedder, 1971), also occurs in fused quartz and in both targets with the more dense aluminum and iron projectiles. Each transition in morphology occurs at impact velocities generating a certain pressure in the target. High density projectiles require a lower velocity than low-density projectiles to generate a given shock pressure.

  7. PREFACE: Dynamic crossover phenomena in water and other glass-forming liquids Dynamic crossover phenomena in water and other glass-forming liquids

    Science.gov (United States)

    Chen, Sow-Hsin; Baglioni, Piero

    2012-02-01

    This special section has been inspired by the workshop on Dynamic Crossover Phenomena in Water and Other Glass-Forming Liquids, held during November 11-13, 2010 at Pensione Bencistà, Fiesole, Italy, a well-preserved 14th century Italian villa tucked high in the hills overlooking Florence. The meeting, an assembly of world renowned scientists, was organized as a special occasion to celebrate the 75th birthday of Professor Sow-Hsin Chen of MIT, a pioneer in several aspects of complex fluids and soft matter physics. The workshop covered a large variety of experimental and theoretical research topics of current interest related to dynamic crossover phenomena in water and, more generally, in other glass-forming liquids. The 30 invited speakers/lecturers and approximately 60 participants were a select group of prominent physicists and chemists from the USA, Europe, Asia and Mexico, who are actively working in the field. Some highlights of this special issue include the following works. Professor Yamaguchi's group and their collaborators present a neutron spin echo study of the coherent intermediate scattering function of heavy water confined in cylindrical pores of MCM-41-C10 silica material in the temperature range 190-298 K. They clearly show that a fragile-to-strong (FTS) dynamic crossover occurs at about 225 K. They attribute the FTS dynamic crossover to the formation of a tetrahedral-like structure, which is preserved in the bulk-like water confined to the central part of the cylindrical pores. Mamontov and Kolesnikov et al study the collective excitations in an aqueous solution of lithium chloride over a temperature range of 205-270 K using neutron and x-ray Rayleigh-Brillouin (coherent) scattering. They detect both the low-frequency and the high-frequency sounds known to exist in pure bulk water above the melting temperature. They also perform neutron (incoherent) and x-ray (coherent) elastic intensity scan measurements. Clear evidence of the crossover in the

  8. On valence electron density, energy dissipation and plasticity of bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Pang, J.J.; Tan, M.J. [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 639798 Singapore (Singapore); Liew, K.M., E-mail: kmliew@cityu.edu.hk [Department of Civil and Architectural Engineering, City University of Hong Kong, Kowloon (Hong Kong)

    2013-11-15

    Highlights: ► Relationship between valence electron density and plasticity of metallic glasses. ► Poisson's ratio increases as electron density decreases. ► Energy dissipation proposed to understand plasticity. ► Low electron density indicates small activation energy. -- Abstract: In conventional crystalline alloys, valence electron density (VED) is one of the most significant factors in determining their phase stability and mechanical properties. Extending the concept to metallic glasses (MGs), it is found, not totally surprisingly, that their mechanical properties are VED-dependent as in crystalline alloys. Interestingly, the whole VED region can be separated into two zones: Zone 1 consists of Mg-, Ca-, and RE-based (RE for rare earth) alloys; Zone 2 consists of the rest of MGs. In either zone, for each type of MGs, Poisson's ratio generally decreases as VED increases. From the energy dissipation viewpoint proposed recently, the amorphous plasticity is closely related to the activation energy for the operation of shear-transformation-zones (STZs). Smaller STZ activation energy suggests higher ductility because STZs with lower activation energy are able to convert deformation work more efficiently into configurational energy rather than heat, which yields mechanical softening and advances the growth of shear bands (SBs). Following this model, it is revealed that the activation energies for STZ operation and crystallization are certainly proportional to VED. Thus, it is understood that, in Zone 2, MGs have a smaller VED and hence lower activation energies which are favorable for ductility and Poisson's ratio. In Zone 1, MGs have the lowest VED but apparent brittleness because either of low glass transition temperature and poor resistance to oxidation or of a large fraction of covalent bonds.

  9. Advanced finite element analysis of die wear in sheet-bulk metal forming processes

    Science.gov (United States)

    Behrens, Bernd-Arno; Bouguecha, Anas; Vucetic, Milan; Chugreev, Alexander; Rosenbusch, Daniel

    2016-10-01

    The novel sheet-bulk metal forming (SBMF) technology allows the production of solid metal components with various functional design features out of flat sheet specimens. However, due to the high working pressures arising during the forming process the efficiency of SBMF is tightly related to the tool service life, which is mainly limited by die wear. In the forming processes involving high contact pressures (e.g. SBMF) the influence of contact normal stresses on the die wear can be overestimated. In order to provide a realistic estimation of the die wear, the shear friction stress must be considered. The presented paper introduces a die wear model that intends the tangential component of contact stress and its implementation in the commercial FE code.

  10. Density and glass forming ability in amorphous atomic alloys: The role of the particle softness

    Science.gov (United States)

    Douglass, Ian; Hudson, Toby; Harrowell, Peter

    2016-04-01

    A key property of glass forming alloys, the anomalously small volume difference with respect to the crystal, is shown to arise as a direct consequence of the soft repulsive potentials between metals. This feature of the inter-atomic potential is demonstrated to be responsible for a significant component of the glass forming ability of alloys due to the decrease in the enthalpy of fusion and the associated depression of the freezing point.

  11. Role and properties of the gel formed during nuclear glass alteration: importance of gel formation conditions

    Science.gov (United States)

    Gin, S.; Ribet, I.; Couillard, M.

    2001-09-01

    A French SON 68 nuclear glass sample was experimentally altered to assess the mechanisms limiting the glass alteration kinetics, especially during the transition phase between the initial rate r0 and the final rate under silicon saturation conditions. A glass specimen was altered at the initial rate for one week to form a silicon-depleted non-protective gel; the specimen was then leached under static conditions at a glass-surface-to-solution-volume ( S/ V) ratio of 500 m-1 and the alteration kinetics were compared with those of a pristine glass specimen altered under the same conditions. Unexpectedly, after static leaching the previously leached glass was 2.7 times as altered as the pristine specimen, and the steady-state silicon concentration was twice as high for the previously leached specimen. STEM characterization of the alteration films showed that the initial non-protective gel constituted a silicon pump with respect to the glass, and that the glass alteration kinetics were limited only when a fraction of the gel became saturated with silicon, and exhibited protective properties. This work also shows that silicon recondensation was uniform at micrometer scale: the silicon hydrolyzed at the reaction interface then diffused before recondensing over a length comparable to the gel thickness. In addition to these findings, this investigation suggests a reinterpretation of the effect of the S/ V ratio on the glass alteration kinetics and on the steady-state dissolved silicon concentration.

  12. Second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass

    DEFF Research Database (Denmark)

    Cao, Q.P.; Li, J.F.; Zhang, P.N.

    2007-01-01

    is estimated to be about 2.46 kJ mol(-1) at 753 K, much smaller than the 61 kJ mol(-1) obtained assuming that it is a polymorphic transformation. It was revealed that the phase transformation occurs through a eutectic crystallization of Cu51Zr14 and Cu2TiZr14 having an effective activation energy of the order......The second amorphous-to-crystalline phase transformation in Cu60Ti20Zr20 bulk metallic glass was investigated by differential scanning calorimetry and x-ray diffractometry. The difference of the Gibbs free energies between the amorphous phase and the crystalline products during the transformation...

  13. Numerical Study of the Effect of the Sample Aspect Ratio on the Ductility of Bulk Metallic Glasses (BMGs) Under Compression

    Science.gov (United States)

    Jiang, Yunpeng

    2016-05-01

    In this article, a systematic numerical study was conducted to study the detailed shear banding evolution in bulk metallic glasses (BMGs) with various sample aspect ratios under uniaxial compression, and whereby the effect of the sample aspect ratio on the compressive ductility was elucidated. A finite strain viscoelastic model was employed to describe the shear banding nucleation, growth, and coalescence in BMG samples with the help of Anand and Su's theory, which was incorporated into the ABAQUS finite element method code as a user material subroutine VUMAT. The present numerical method was first verified by comparing with the corresponding experimental results, and then parameter analysis was performed to discuss the impact of microstructure parameters on the predicted results. The present modeling will shed some light on enhancing the toughness of BMG structures in the engineering applications.

  14. On the mechanically induced crystallization of FCC phases by mechanical milling in ZrAlNiCu bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jiang [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian 116024 (China); Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, F57012 Metz Cedex (France); Grosdidier, Thierry, E-mail: grosdidier@letam.sciences.univ-metz.f [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, F57012 Metz Cedex (France); Allain-Bonasso, Nathalie [Laboratoire d' Etude des Textures et Applications aux Materiaux (LETAM, CNRS 3143), Universite Paul Verlaine-Metz, Ile du Saulcy, F57012 Metz Cedex (France); Gaffet, Eric [Nanomaterials Research Group (NRG, UMR CNRS 5060), Site de Sevenans (UTBM), F90010 Belfort Cedex (France); Dong, Chuang [Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian 116024 (China)

    2010-08-15

    In the present study, amorphous-nanocrystalline phase transformation induced by mechanical milling of full monolithic bulk metallic glasses (based on Zr{sub 65}Al{sub 7.5}Ni{sub 10}Cu{sub 17.5} and Zr{sub 58}Al{sub 16}Ni{sub 11}Cu{sub 15} alloys) has been investigated using X-ray diffraction as well as transmission electron microscopy. Nanocrystals having an FCC structure and a grain size of several 10 nm precipitate in the early stages of the milling process and remain stable for long milling duration. The structure changes induced by milling give a new insight on the preparation of amorphous-related alloys when using the method of mechanical milling.

  15. Light Emission and Dynamic Failure Mechanism of Hypervelocity Impact on Zr-Ti-Ni-Cu-Be Bulk Metallic Glass

    Science.gov (United States)

    Sun, Bao-Ru; Zhan, Zai-Ji; Liang, Bo; Zhang, Rui-Jun; Wang, Wen-Kui

    2011-09-01

    Hypervelocity impact on rectangular plate-shaped Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) is performed by a two-stage light gas gun. The targets used in the experiment are BMG plates with a thickness of 5 mm. The projectile, spherical aluminum (3.1 mm in diameter), is accelerated up to various velocities; the light is detected with a radiometer. The emission lasts from 200 μs up to 1500 μs and the intensity increases from 44 to 900 W/(Sr·μm). The duration and intensity of a light emission seem to depend on the impact velocity and the extent of target destruction through the formation of impact craters or penetration.

  16. Dry Sliding Wear Behavior of Spark Plasma Sintered Fe-Based Bulk Metallic Glass/Graphite Composites

    Directory of Open Access Journals (Sweden)

    Xiulin Ji

    2016-09-01

    Full Text Available Bulk metallic glass (BMG and BMG-graphite composites were fabricated using spark plasma sintering at the sintering temperature of 575 °C and holding time of 15 min. The sintered composites exhibited partial crystallization and the presence of distributed porosity and graphite particles. The effect of graphite reinforcement on the tribological properties of the BMG/graphite composites was investigated using dry ball-on-disc sliding wear tests. The reinforcement of graphite resulted in a reduction in both the wear rate and the coefficient of friction as compared to monolithic BMG samples. The wear surfaces of BMG/graphite composites showed regions of localized wear loss due to microcracking and fracture, as was also the case with the regions covered with graphite-rich protective film due to smearing of pulled off graphite particles.

  17. Correlation between the microstructures and the deformation mechanisms of CuZr-based bulk metallic glass composites

    Directory of Open Access Journals (Sweden)

    K. K. Song

    2013-01-01

    Full Text Available The variation of the transformation-mediated deformation behavior with microstructural changes in CuZr-based bulk metallic glass composites is investigated. With increasing crystalline volume fraction, the deformation mechanism gradually changes from a shear-banding dominated process as evidenced by a chaotic serrated flow behavior, to being governed by a martensitic transformation with a pronounced elastic-plastic stage, resulting in different plastic deformations evolving into a self-organized critical state characterized by the power-law distribution of shear avalanches. This is reflected in the stress-strain curves by a single-to-“double”-to-“triple”-double yielding transition and by different mechanical properties with different serrated flow characteristics, which are interpreted based on the microstructural evolutions and a fundamental energy theorem. Our results can assist in understanding deformation behaviors for high-performance metastable alloys.

  18. Correlation between the microstructures and the deformation mechanisms of CuZr-based bulk metallic glass composites

    Science.gov (United States)

    Song, K. K.; Pauly, S.; Sun, B. A.; Tan, J.; Stoica, M.; Kühn, U.; Eckert, J.

    2013-01-01

    The variation of the transformation-mediated deformation behavior with microstructural changes in CuZr-based bulk metallic glass composites is investigated. With increasing crystalline volume fraction, the deformation mechanism gradually changes from a shear-banding dominated process as evidenced by a chaotic serrated flow behavior, to being governed by a martensitic transformation with a pronounced elastic-plastic stage, resulting in different plastic deformations evolving into a self-organized critical state characterized by the power-law distribution of shear avalanches. This is reflected in the stress-strain curves by a single-to-"double"-to-"triple"-double yielding transition and by different mechanical properties with different serrated flow characteristics, which are interpreted based on the microstructural evolutions and a fundamental energy theorem. Our results can assist in understanding deformation behaviors for high-performance metastable alloys.

  19. Transparent phosphosilicate glasses containing crystals formed during cooling of melts

    DEFF Research Database (Denmark)

    Liu, S. J.; Zhang, Yanfei; He, W.;

    2011-01-01

    The effect of P2O5-SiO2 substitution on spontaneous crystallization of SiO2-Al2O3-P2O5- Na2O-MgO melts during cooling was studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and rotation viscometry. Results show that addition of P2O5 lea...... Na2MgSiO4 is also enhanced during cooling of the melts. In addition, the sizes of the local crystalline and separated glassy domains are smaller than the wavelength of the visible light, and this leads to the transparency of the obtained glasses containing crystals....

  20. Structural and Mechanical Characterization of Zr58.5Ti8.2Cu14.2Ni11.4Al7.7 Bulk Metallic Glass

    Directory of Open Access Journals (Sweden)

    Jürgen Eckert

    2011-12-01

    Full Text Available Thermal stability, structure and mechanical properties of the multi-component Zr58.5Ti8.2Cu14.2Ni11.4Al7.7 bulk metallic glass have been studied in detail. The glassy material displays good thermal stability against crystallization and a fairly large supercooled liquid region of 52 K. During heating, the alloy transforms into a metastable icosahedral quasicrystalline phase in the first stage of crystallization. At high temperatures, the quasicrystalline phase undergoes a transformation to form tetragonal and cubic NiZr2-type phases. Room-temperature compression tests of the as-cast sample show good mechanical properties, namely, high compressive strength of about 1,630 MPa and fracture strain of 3.3%. This is combined with a density of 6.32 g/cm3 and values of Poisson’s ratio and Young’s modulus of 0.377 and 77 GPa, respectively. The mechanical properties of the glass can be further improved by cold rolling. The compressive strength rises to 1,780 MPa and the fracture strain increases to 8.3% for the material cold-rolled to a diameter reduction of 10%.

  1. Asymmetric crystallization upon heating and cooling in model glass-forming systems

    Science.gov (United States)

    Wang, Minglei; Zhang, Kai; Liu, Yanhui; Schroers, Jan; Shattuck, Mark; O'Hern, Corey

    2014-03-01

    We perform molecular dynamics simulations of binary Lennard-Jones (LJ) and hard-sphere (HS) systems to understand the asymmetry in the critical cooling and heating rates for crystallization observed in experiments on bulk metallic glasses, where much faster heating rates are required to prevent crystallization. For the LJ systems, we cool the systems at different rates (above the critical cooling rate Rc) to temperatures below the glass transition, and subsequently begin heating the samples at different rates to measure the critical heating rate Rh below which the system crystallizes. We perform companion studies of HS systems, except we measure the asymmetry in the critical compression and dilation rates to enhance the asymmetry. We show that the asymmetry increases with the glass-formability of the binary mixtures and explain this result by characterizing the structural order of the systems.

  2. Kinetic analysis of the non-isothermal crystallization process, magnetic and mechanical properties of FeCoBSiNb and FeCoBSiNbCu bulk metallic glasses

    Science.gov (United States)

    Ramasamy, Parthiban; Stoica, Mihai; Taghvaei, A. H.; Prashanth, K. G.; Ravi Kumar, Eckert, Jürgen

    2016-02-01

    The crystallization kinetics of [(Fe0.5Co0.5)0.75B0.2Si0.05]96Nb4 and {[(Fe0.5Co0.5)0.75B0.2Si0.05]0.96Nb0.04}99.5Cu0.5 bulk metallic glasses were evaluated using differential scanning calorimetry under non-isothermal condition. The fully glassy rods with diameters up to 2 mm were obtained by copper mold injection casting. Both glasses show good thermal stability, but the addition of only 0.5% Cu completely changes the crystallization behavior. The average activation energy required for crystallization decreases from 645 kJ/mol to 425 kJ/mol after Cu addition. Upon heating, the Cu-free alloy forms only the metastable Fe23B6 phase. In contrast, two well-separated exothermic events are observed for the Cu-added bulk glassy samples. First, the (Fe,Co) phase nucleates and then (Fe,Co)2B and/or (Fe,Co)3B crystallize from the remaining glassy matrix. The Cu-added alloy exhibits a lower coercivity and a higher magnetic saturation than the base alloy, both in as-cast as well as in annealed condition. Besides, the Cu-added glassy sample with 2 mm diameter exhibits a maximum compressive fracture strength of 3913 MPa together with a plastic strain of 0.6%, which is highest plastic strain ever reported for 2 mm diameter ferromagnetic bulk metallic glass sample. Although Cu addition improves the magnetic and mechanical properties of the glass, it affects the glass-forming ability of the base alloy.

  3. Molecular weight dependence of surface flow near the bulk glass transition temperature

    Science.gov (United States)

    Chai, Yu; Salez, Thomas; Benzaquen, Michael; Raphael, Elie; Forrest, James A.

    2014-03-01

    We present the study on molecular weight dependent sub-Tg surface dynamics of polymer thin films by using the Nano-step experiment [McGraw et al. Soft Matter 7, 7832 (2011)]. By varying the molecular weight, we are able to probe the surface dynamics of the free surface below Tg with the polymer size comparable to the surface depth. In particular, we define and use a correlation function to compare measured and calculated profiles to analyze the transition from the bulk flow to flow restricted to the surface region. Surprisingly, even for the polymers with Mw = 22,000 surface flow is still observed below the bulk Tg value. A numerical simulation of random walk is used to find the fraction of polymer of which all of the polymer segments are located in the free surface region. The simulation results indicate that there are still a significant fraction of polymer molecules where all segments are in the near free surface region. These molecules can undergo flow consistent with the experimental results.

  4. Manufacturing Solid Dosage Forms from Bulk Liquids Using the Fluid-bed Drying Technology.

    Science.gov (United States)

    Qi, Jianping; Lu, Y I; Wu, Wei

    2015-01-01

    Solid dosage forms are better than liquid dosage forms in many ways, such as improved physical and chemical stability, ease of storage and transportation, improved handling properties, and patient compliance. Therefore, it is required to transform dosage forms of liquid origins into solid dosage forms. The functional approaches are to absorb the liquids by solid excipients or through drying. The conventional drying technologies for this purpose include drying by heating, vacuum-, freeze- and spray-drying, etc. Among these drying technologies, fluidbed drying emerges as a new technology that possesses unique advantages. Fluid-bed drying or coating is highly efficient in solvent removal, can be performed at relatively low temperatures, and is a one-step process to manufacture formulations in pellet forms. In this article, the status of the art of manufacturing solid dosage forms from bulk liquids by fluid-bed drying technology was reviewed emphasizing on its application in solid dispersion, inclusion complexes, self-microemulsifying systems, and various nanoscale drug delivery systems.

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

    Science.gov (United States)

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

    2010-12-01

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

  6. Spectrophotometric Determination of drugs in bulk and pharmaceutical dosage forms by using Tetracyanoethylene

    Directory of Open Access Journals (Sweden)

    Bathini.Srinivas

    2015-06-01

    Full Text Available A selective ,sensitive ,accurate UV-Visible spectrophotometric methods have been developed for the estimation of drugs viz.,Diflunisal (DFL,Febuxostat(FBT,Metaxalone(MTX,Fexofenadine methyl ester(FME and Linezolid(LZD in bulk and their pharmaceutical dosage forms using Tetracyanoethylene (TCNE as analytical reagent. These method are based on the formation of charge transfer complexes of drugs as n-electron donor with TCNE as π-acceptor .The selected drugs turned the colorless solution of TCNE in Acetonytrile to yellow and exhibited a doublet at 400 & 420nm due to the formation of Complex of drugs with TCNE.Under the optimized experimental conditions ,Beer, s law is obeyed over the concentration ranges of 10-50 μg/ml ,5- 25 μg/ml,15-75 μg/ml,5-25 μg/ml and 5-25 μg/ml for DFL,FBT,MTX,FME and LZD respectively. The effect of reagent concentrations, polarity of solvents and effect of reaction time have been studied and optimized. These methods have been validated in terms of ICH guidelines and applied to the quantification of selected drugs in bulk and dosage forms.

  7. Estimation Based on Emission Wavelength of Dabigatran Etexilate Mesylate in Bulk and Capsule Dosage Form

    Science.gov (United States)

    Anumolu, P. D.; Satyanarayana, M.; Gayatri, T.; Praveena, M.; Sunitha, G.; Subrahmanyam, C.V.S.

    2016-01-01

    A simple, rapid, specific and highly sensitive spectrofluorimetric method has been developed for the quantification of dabigatran etexilate mesylate in bulk and capsule dosage form. A linear relationship was found between fluorescence intensity and concentration in the range of 0.01-1.0 μg/ml in dimethyl sulphoxide as solvent at an emission wavelength of 391 nm after excitation at 334 nm, with a good correlation coefficient (0.989). The detection and quantification limits were found to be 0.005 and 0.015 μg/ml, respectively. The proposed method was applied for dabigatran etexilate mesylate capsules, results reveal with percentage recovery of 102% and percentage relative standard deviation values were found to be less than 2 for accuracy and precision studies. The proposed method was validated for linearity, range, accuracy, precision, limit of detection and quantification according to International Conference on Harmonization guidelines. Statistical analysis of the results revealed high accuracy and good precision. The suggested procedures could be used for the determination of dabigatran etexilate mesylate in bulk and capsule dosage form in quality control laboratories of industries as well as in academic institutions. PMID:27168697

  8. Investigation of the microcrack evolution in a Ti-based bulk metallic glass matrix composite

    Directory of Open Access Journals (Sweden)

    Yongsheng Wang

    2014-04-01

    Full Text Available The initiation and evolution behavior of the shear-bands and microcracks in a Ti-based metallic-glass–matrix composite (MGMC were investigated by using an in-situ tensile test under transmission electron microscopy (TEM. It was found that the plastic deformation of the Ti-based MGMC related with the generation of the plastic deformation zone in crystalline and shear deformation zone in glass phase near the crack tip. The dendrites can suppress the propagation of the shear band effectively. Before the rapid propagation of cracks, the extending of plastic deformation zone and shear deformation zone ahead of crack tip is the main pattern in the composite.

  9. Use of Numerical Simulation at Optimisation of Technological Processes of Cold Bulk Forming

    Directory of Open Access Journals (Sweden)

    Stanislav RUSZ

    2012-06-01

    Full Text Available The paper deals with numerical and physical modelling aimed at optimisation of production technology and designing of manufacturing tools with use of finite-element method. For the topic of cold bulk forming a manufacture of pressed insert, used in industry as a component for damping system for passenger cars, was simulated. It is a rotationally symmetric component, which is subjected to high axial load, and strength and fatigue characteristics of which depend substantially on service life and reliability of the whole damping system. This component was subjected to analysis of distribution of flow stress and deformation intensity at combined extrusion from the viewpoint of their load with use of simulating software Simufact.Forming 10.0. The simulation process ran smoothly, without sudden changes of the shape leading to formation of possible internal defects.

  10. Determination of the Structure of Vitrified Hydroceramic/CBC Waste Form Glasses Manufactured from DOE Reprocessing Waste

    Energy Technology Data Exchange (ETDEWEB)

    Scheetz, B.E.; White, W. B.; Chesleigh, M.; Portanova, A.; Olanrewaju, J.

    2005-05-31

    The selection of a glass-making option for the solidification of nuclear waste has dominated DOE waste form programs since the early 1980's. Both West Valley and Savannah River are routinely manufacturing glass logs from the high level waste inventory in tank sludges. However, for some wastes, direct conversion to glass is clearly not the optimum strategy for immobilization. INEEL, for example, has approximately 4400 m{sup 3} of calcined high level waste with an activity that produces approximately 45 watts/m{sup 3}, a rather low concentration of radioactive constituents. For these wastes, there is value in seeking alternatives to glass. An alternative approach has been developed and the efficacy of the process demonstrated that offers a significant savings in both human health and safety exposures and also a lower cost relative to the vitrification option. The alternative approach utilizes the intrinsic chemical reactivity of the highly alkaline waste with the addition of aluminosilicate admixtures in the appropriate proportions to form zeolites. The process is one in which a chemically bonded ceramic is produced. The driving force for reaction is derived from the chemical system itself at very modest temperatures and yet forms predominantly crystalline phases. Because the chemically bonded ceramic requires an aqueous medium to serve as a vehicle for the chemical reaction, the proposed zeolite-containing waste form can more adequately be described as a hydroceramic. The hydrated crystalline materials are then subject to hot isostatic pressing (HIP) which partially melts the material to form a glass ceramic. The scientific advantages of the hydroceramic/CBC approach are: (1) Low temperature processing; (2) High waste loading and thus only modest volumetric bulking from the addition of admixtures; (3) Ability to immobilize sodium; (4) Ability to handle low levels of nitrate (2-3% NO{sub 3}{sup -}); (5) The flexibility of a vitrifiable waste; and (6) A process

  11. Super-plasticity of Zr64.80Cu14.85Ni10.35Al10 bulk metallic glass at room temperature

    Institute of Scientific and Technical Information of China (English)

    TAO PingJun; YANG YuanZheng; BAI XiaoJun; XIE ZhiWei; CHEN XianCao; DONG ZhenJiang; Wen JianGuo

    2008-01-01

    Generally, bulk metallic glasses (BMGs) exhibit a very limited plastic deformation under a compression load at room temperature, often less than 2% before fracturing. In this letter, through an appropriate choice of BMGs' composition, an amorphous rod of Zr64.80Cu14.85Ni10.35Al10 with a diameter of 2 mm was prepared by using copper mold suction casting. X-ray diffraction and differential scanning calorimetry were utilized to determine its structure and thermal stability, and the uniaxial compression test was adopted to study its plastic deformation behavior at room temperature simultaneously. The results showed that the glass transition temperature and onset temperature of the exothermic reaction of the amorphous rod were 646 and 750 K, respectively, and its micro-hardness was 594.7 Hv. During com-pression, when the engineering strain and engineering stress arrived at 9.05% and 1732 MPa, respec-tively, i.e., the true strain and true stress reached 9.42% and 1560 MPa, respectively, the amorphous rod started to yield. After yielding, with the increase of load, the strain increased and the glass rod ulti-mately were compressed into flake-like form. Although the maximum engineering strain was larger than 70%, i.e., the maximum true strain exceeded by 120%, the amorphous specimen was not fractured, indicating that it has super-plasticity at room temperature. Through the appropriate choice of compo-sition and optimization of the technological process, flexible BMG with super-plasticity at room tem-perature could be produced.

  12. Crystal growth nucleation and Fermi energy equalization of intrinsic spherical nuclei in glass-forming melts

    Directory of Open Access Journals (Sweden)

    Robert F Tournier

    2009-01-01

    Full Text Available The energy saving resulting from the equalization of Fermi energies of a crystal and its melt is added to the Gibbs free-energy change ΔG2ls associated with a crystal formation in glass-forming melts. This negative contribution being a fraction ε ls(T of the fusion heat is created by the electrostatic potential energy −U0 resulting from the electron transfer from the crystal to the melt and is maximum at the melting temperature Tm in agreement with a thermodynamics constraint. The homogeneous nucleation critical temperature T2, the nucleation critical barrier ΔG2ls*/kBT and the critical radius R*2ls are determined as functions of εls(T. In bulk metallic glass forming melts, εls(T and T2 only depend on the free-volume disappearance temperature T0l, and εls(Tm is larger than 1 (T0l>Tm/3; in conventional undercooled melts εls(Tm is smaller than 1 (T0l>Tm/3. Unmelted intrinsic crystals act as growth nuclei reducing ΔG2ls*/kBT and the nucleation time. The temperature-time transformation diagrams of Mg65Y10 Cu25, Zr41.2Ti13.8 Cu12.5Ni10Be22.5, Pd43Cu27 Ni10P20, Fe83B17 and Ni melts are predicted using classic nucleation models including time lags in transient nucleation, by varying the intrinsic nucleus contribution to the reduction of ΔG2ls*/kBT. The energy-saving coefficient ε nm(T of an unmelted crystal of radius Rnm is reduced when Rnm LtR*2ls; εnm is quantified and corresponds to the first energy level of one s-electron moving in vacuum in the same spherical attractive potential −U0 despite the fact that the charge screening is built by many-body effects.

  13. Dynamical heterogeneity in a glass-forming ideal gas.

    Science.gov (United States)

    Charbonneau, Patrick; Das, Chinmay; Frenkel, Daan

    2008-07-01

    We conduct a numerical study of the dynamical behavior of a system of three-dimensional "crosses," particles that consist of three mutually perpendicular line segments of length sigma rigidly joined at their midpoints. In an earlier study [W. van Ketel, Phys. Rev. Lett. 94, 135703 (2005)] we showed that this model has the structural properties of an ideal gas, yet the dynamical properties of a strong glass former. In the present paper we report an extensive study of the dynamical heterogeneities that appear in this system in the regime where glassy behavior sets in. On the one hand, we find that the propensity of a particle to diffuse is determined by the structure of its local environment. The local density around mobile particles is significantly less than the average density, but there is little clustering of mobile particles, and the clusters observed tend to be small. On the other hand, dynamical susceptibility results indicate that a large dynamical length scale develops even at moderate densities. This suggests that propensity and other mobility measures are an incomplete measure of the dynamical length scales in this system.

  14. Summary Report: Glass-Ceramic Waste Forms for Combined Fission Products

    Energy Technology Data Exchange (ETDEWEB)

    Crum, Jarrod V.; Riley, Brian J.; Turo, Laura A.; Tang, Ming; Kossoy, Anna

    2011-09-23

    Glass-ceramic waste form development began in FY 2010 examining two combined waste stream options: (1) alkaline earth (CS) + lanthanide (Ln), and (2) + transition metal (TM) fission-product waste streams generated by the uranium extraction (UREX+) separations process. Glass-ceramics were successfully developed for both options however; Option 2 was selected over Option 1, at the conclusion of 2010, because Option 2 immobilized all three waste streams with only a minimal decrease in waste loading. During the first year, a series of three glass (Option 2) were fabricated that varied waste loading-WL (42, 45, and 50 mass%) at fixed molar ratios of CaO/MoO{sub 3} and B{sub 2}O{sub 3}/alkali both at 1.75. These glass-ceramics were slow cooled and characterized in terms of phase assemblage and preliminary irradiation stability. This fiscal year, further characterization was performed on the FY 2010 Option 2 glass-ceramics in terms of: static leach testing, phase analysis by transmission electron microscopy (TEM), and irradiation stability (electron and ion). Also, a new series of glass-ceramics were developed for Option 2 that varied the additives: Al{sub 2}O{sub 3} (0-6 mass%), molar ratio of CaO/MoO{sub 3} and B{sub 2}O{sub 3}/alkali (1.75 to 2.25) and waste loading (50, 55, and 60 mass%). Lastly, phase pure powellite and oxyapatite were synthesized for irradiation studies. Results of this fiscal year studies showed compositional flexibility, chemical stability, and radiation stability in the current glass-ceramic system. First, the phase assemblages and microstructure of all of the FY 2010 and 2011 glass-ceramics are very similar once subjected to the slow cool heat treatment. The phases identified in these glass-ceramics were oxyapatite, powellite, cerianite, and ln-borosilicate. This shows that variations in waste loading or additives can be accommodated without drastically changing the phase assemblage of the waste form, thus making the processing and performance

  15. Stability-indicating HPTLC determination of ambroxol hydrochloride in bulk drug and pharmaceutical dosage form.

    Science.gov (United States)

    Jain, P S

    2010-01-01

    A simple, selective, precise, and stability-indicating high-performance thin-layer chromatographic (HPTLC) method for the analysis of ambroxol hydrochloride both as a bulk drug and in formulations was developed and validated. The method employed HPTLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of methanol-triethylamine (4:6 v/v). The system was found to give a compact spot for ambroxol hydrochloride (R(f) value of 0.53 +/- 0.02). Densitometric analysis of ambroxol hydrochloride was carried out in the absorbance mode at 254 nm. The linear regression analysis data for the calibration plots showed good linear relationship with r(2) = 0.9966 +/- 0.0013 with respect to peak area in the concentration range 100-1000 ng/spot. The mean value +/- standard deviation of slope and intercept were 164.85 +/- 0.72 and 1168.3 +/- 8.26 with respect to peak area. The method was validated for precision, recovery, and robustness. The limits of detection and quantitation were 10 and 30 ng/spot, respectively. Ambroxol hydrochloride was subjected to oxidation and thermal degradation. The drug undergoes degradation under oxidation and heat conditions. This indicates that the drug is susceptible to oxidation and heat. Statistical analysis proves that the method is repeatable, selective, and accurate for the estimation of said drug. Stability indicating of new chemical entities is an important part for the drug development of ambroxol hydrochloride and for its estimation in plasma and other biological fluids; the novel Statistical analysis proves that the method is repeatable and selective for the analysis of ambroxol hydrochloride as bulk drug and in pharmaceutical formulations. The proposed developed HPTLC method can be applied for identification and quantitative determination of ambroxol hydrochloride in bulk drug and dosage forms. This work is to determine the purity of the drug available from the various sources by detecting

  16. Endoscopic fringe projection for in-situ inspection of a sheet-bulk metal forming process

    Science.gov (United States)

    Matthias, Steffen; Kästner, Markus; Reithmeier, Eduard

    2015-05-01

    Sheet-bulk metal forming is a new production process capable of performing deep-drawing and massive forming steps in a single operation. However, due to the high forming forces of the forming process, continuous process control is required in order to detect wear on the forming tool before production quality is impacted. To be able to measure the geometry of the forming tool in the limited space of forming presses, a new inspection system is being developed within the SFB/TR 73 collaborative research center. In addition to the limited space, the process restricts the amount of time available for inspection. Existing areal optical measurement systems suffer from shadowing when measuring the tool's inner elements, as they cannot be placed in the limited space next to the tool, while tactile measurement systems cannot meet the time restrictions for measuring the areal geometries. The new inspection system uses the fringe projection optical measurement principle to capture areal geometry data from relevant parts of the forming tool in short time. Highresolution image fibers are used to connect the system's compact sensor head to a base unit containing both camera and projector of the fringe projection system, which can be positioned outside of the moving parts of the press. To enable short measurement times, a high intensity laser source is used in the projector in combination with a digital micro-mirror device. Gradient index lenses are featured in the sensor head to allow for a very compact design that can be used in the narrow space above the forming tool inside the press. The sensor head is attached to an extended arm, which also guides the image fibers to the base unit. A rotation stage offers the possibility to capture measurements of different functional elements on the circular forming tool by changing the orientation of the sensor head next to the forming tool. During operation of the press, the arm can be travelled out of the moving parts of the forming press

  17. Glass Forming Ability of Amorphous Drugs Investigated by Continuous Cooling and Isothermal Transformation.

    Science.gov (United States)

    Blaabjerg, Lasse I; Lindenberg, Eleanor; Löbmann, Korbinian; Grohganz, Holger; Rades, Thomas

    2016-09-06

    The aim of this study was to investigate the glass forming ability of 12 different drugs by the determination of continuous cooling and isothermal transformation diagrams in order to elucidate if an inherent differentiation between the drugs with respect to their the glass forming ability can be made. Continuous-cooling-transformation (CCT) and time-temperature-transformation (TTT) diagrams of the drugs were developed in order to predict the critical cooling rate necessary to convert the drug from the melt into an amorphous form. While TTT diagrams overestimated the actual critical cooling rate, they allowed an inherent differentiation of glass forming ability for the investigated drugs into drugs that are extremely difficult to amorphize (>750 °C/min), drugs that require modest cooling rates (>10 °C/min), and drugs that can be made amorphous even at very slow cooling rates (>2 °C/min). Thus, the glass forming ability can be predicted by the use of TTT diagrams. In contrast to TTT diagrams, CCT diagrams may not be suitable for small organic molecules due to poor separation of exothermic events, which makes it difficult to determine the zone of recrystallization. In conclusion, this study shows that glass forming ability of drugs can be predicted by TTT diagrams.

  18. Pressure effect on crystallization kinetics in Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Gerward, Leif; Xu, Y.S.

    2002-01-01

    Crystallization kinetics of a Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass in the supercooled liquid region have been investigated by performing in situ high-temperature and high-pressure x-ray diffraction measurements using synchrotron radiation. A pressure-time-temperature-transformation diagram...

  19. Communication: Non-Newtonian rheology of inorganic glass-forming liquids: Universal patterns and outstanding questions

    Science.gov (United States)

    Zhu, W.; Aitken, B. G.; Sen, S.

    2017-02-01

    All families of inorganic glass-forming liquids display non-Newtonian rheological behavior in the form of shear thinning at high shear rates. Experimental evidence is presented to demonstrate the existence of remarkable universality in this behavior, irrespective of chemical composition, structure, topology, and viscosity. However, contrary to intuition, in all cases the characteristic shear rates that mark the onset of shear thinning in these liquids are orders of magnitude slower than the global shear relaxation rates. Attempt is made to reconcile such differences within the framework of the cooperative structural relaxation model of glass-forming liquids.

  20. Sub-Tg features of glasses formed by cooling glycerol under pressure - Additional incompatibility of vibrational with configurational states in the depressurized, high density glass

    Science.gov (United States)

    Andersson, Ove; Johari, G. P.

    2016-11-01

    The vibrational state of a glass is naturally incompatible with its configurational state, which makes the glass structurally unstable. When a glass is kept at constant temperature, both the vibrational and configurational states of a glass change with time until it becomes metastable (equilibrium) liquid and the two states become compatible. The process, known as structural relaxation, occurs at a progressively higher rate during heating, and the properties of a glass change accordingly. We add to this incompatibility by depressurizing a glass that had been formed by cooling a liquid under a high pressure, p, and then investigate the effects of the added incompatibility by studying thermal conductivity, κ , and the heat capacity per unit volume ρ Cp of the depressurized glass. We use glycerol for the purpose and study first the changes in the features of κ and of ρ Cp during glass formation on cooling under a set of different p. We then partially depressurize the glass and study the effect of the p-induced instability on the features of κ and ρ Cp as the glass is isobarically heated to the liquid state. At a given low p, the glass configuration that was formed by cooling at high-p had a higher κ than the glass configuration that was formed by cooling at a low p. The difference is more when the glass is formed at a higher p and/or is depressurized to a lower p. On heating at a low p, its κ decreases before its glass-liquid transition range is reached. The effect is the opposite of the increase in κ observed on heating a glass at the same p under which it was formed. It is caused by thermally assisted loss of the added incompatibility of configurational and vibrational states of a high-p formed glass kept at low p. If a glass formed under a low-p is pressurized and then heated under high p, it would show the opposite effect, i.e., its κ would first increase to its high p value before its glass-to-liquid transition range.

  1. Physical stability of drugs after storage above and below the glass transition temperature: Relationship to glass-forming ability.

    Science.gov (United States)

    Alhalaweh, Amjad; Alzghoul, Ahmad; Mahlin, Denny; Bergström, Christel A S

    2015-11-10

    Amorphous materials are inherently unstable and tend to crystallize upon storage. In this study, we investigated the extent to which the physical stability and inherent crystallization tendency of drugs are related to their glass-forming ability (GFA), the glass transition temperature (Tg) and thermodynamic factors. Differential scanning calorimetry was used to produce the amorphous state of 52 drugs [18 compounds crystallized upon heating (Class II) and 34 remained in the amorphous state (Class III)] and to perform in situ storage for the amorphous material for 12h at temperatures 20°C above or below the Tg. A computational model based on the support vector machine (SVM) algorithm was developed to predict the structure-property relationships. All drugs maintained their Class when stored at 20°C below the Tg. Fourteen of the Class II compounds crystallized when stored above the Tg whereas all except one of the Class III compounds remained amorphous. These results were only related to the glass-forming ability and no relationship to e.g. thermodynamic factors was found. The experimental data were used for computational modeling and a classification model was developed that correctly predicted the physical stability above the Tg. The use of a large dataset revealed that molecular features related to aromaticity and π-π interactions reduce the inherent physical stability of amorphous drugs.

  2. Structural origin of fractional Stokes-Einstein relation in glass-forming liquids

    Science.gov (United States)

    Pan, Shaopeng; Wu, Z. W.; Wang, W. H.; Li, M. Z.; Xu, Limei

    2017-01-01

    In many glass-forming liquids, fractional Stokes-Einstein relation (SER) is observed above the glass transition temperature. However, the origin of such phenomenon remains elusive. Using molecular dynamics simulations, we investigate the break- down of SER and the onset of fractional SER in a model of metallic glass-forming liquid. We find that SER breaks down when the size of the largest cluster consisting of trapped atoms starts to increase sharply at which the largest cluster spans half of the simulations box along one direction, and the fractional SER starts to follows when the largest cluster percolates the entire system and forms 3-dimentional network structures. Further analysis based on the percolation theory also confirms that percolation occurs at the onset of the fractional SER. Our results directly link the breakdown of the SER with structure inhomogeneity and onset of the fraction SER with percolation of largest clusters, thus provide a possible picture for the break- down of SER and onset of fractional SER in glass-forming liquids, which is is important for the understanding of the dynamic properties in glass-forming liquids.

  3. Structural origin of fractional Stokes-Einstein relation in glass-forming liquids

    Science.gov (United States)

    Pan, Shaopeng; Wu, Z. W.; Wang, W. H.; Li, M. Z.; Xu, Limei

    2017-01-01

    In many glass-forming liquids, fractional Stokes-Einstein relation (SER) is observed above the glass transition temperature. However, the origin of such phenomenon remains elusive. Using molecular dynamics simulations, we investigate the break- down of SER and the onset of fractional SER in a model of metallic glass-forming liquid. We find that SER breaks down when the size of the largest cluster consisting of trapped atoms starts to increase sharply at which the largest cluster spans half of the simulations box along one direction, and the fractional SER starts to follows when the largest cluster percolates the entire system and forms 3-dimentional network structures. Further analysis based on the percolation theory also confirms that percolation occurs at the onset of the fractional SER. Our results directly link the breakdown of the SER with structure inhomogeneity and onset of the fraction SER with percolation of largest clusters, thus provide a possible picture for the break- down of SER and onset of fractional SER in glass-forming liquids, which is is important for the understanding of the dynamic properties in glass-forming liquids. PMID:28059111

  4. HPLC METHOD DEVELOPMENT OF AMLODIPINE BY RP-HPLC IN ITS BULK DOSAGE FORMS

    Directory of Open Access Journals (Sweden)

    V. Naveen Kumar, K. Kiran kumar, P. Ramesh Babu, K. Anilkumar

    2012-06-01

    Full Text Available A new, simple, precise, sensitive, accurate and reproducible Reverse phase HPLC method was developed and validated for the analysis of amlodipine in bulk dosage forms. The separation was conducted by using c-18 RP-HPLC coloumn, which was maintained at ambient temperature. The mobile phase consisting of Phosphate buffer and Acetonitrile (90:10v/v was delivered at a rate of 1.5 ml/min. The analysis was detected by using UV detector at the wave length of 225nm.The method is validated for its specificity, precision, accuracy, linearity and robustness. The method was found to be linear over the concentration range 10-100 g/ml (r2 =0.999. The retention time for amlodipine was found to be 3.34min. Limit of quantification of the method is 0.179g/ml and limit of detection is 0.054 g/ml.

  5. Linking Equilibrium and Nonequilibrium Dynamics in Glass-Forming Systems

    DEFF Research Database (Denmark)

    Mauro, John C.; Guo, Xiaoju; Smedskjær, Morten Mattrup

    , we show that the nonequilibrium glassy dynamics are intimately connected with the equilibrium liquid dynamics. This is accomplished by deriving a new functional form for the thermal history dependence of nonequilibrium viscosity, which is validated against experimental measurements of industrial......Understanding nonequilibrium glassy dynamics is of great scientific and technological importance. However, prediction of the temperature, thermal history, and composition dependence of nonequilibrium viscosity is challenging due to the noncrystalline and nonergodic nature of the glassy state. Here...

  6. On the induction of homogeneous bulk crystallization in Eu-doped calcium aluminosilicate glass by applying simultaneous high pressure and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Muniz, R. F., E-mail: robsonfmuniz@yahoo.com.br [Institut Lumière Matière, UMR 5306 CNRS-Université Lyon 1, Université de Lyon, 69622 Villeurbanne (France); Departamento de Física, Universidade Estadual de Maringá, 87020900, Maringá, PR (Brazil); Ligny, D. de [Department of Materials Science, Glass and Ceramics, University of Erlangen Nürnberg, Martensstr. 5, 91058 Erlangen (Germany); Le Floch, S.; Martinet, C.; Guyot, Y. [Institut Lumière Matière, UMR 5306 CNRS-Université Lyon 1, Université de Lyon, 69622 Villeurbanne (France); Rohling, J. H.; Medina, A. N.; Sandrini, M.; Baesso, M. L. [Departamento de Física, Universidade Estadual de Maringá, 87020900, Maringá, PR (Brazil); Andrade, L. H. C.; Lima, S. M. [Grupo de Espectroscopia Óptica e Fototérmica, Universidade Estadual de Mato Grosso do Sul, C.P. 351, Dourados, MS (Brazil)

    2016-06-28

    From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca{sub 3}Mg(SiO{sub 4}){sub 2}] and diopside [CaMgSi{sub 2}O{sub 6}]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f{sup 6}5d{sup 1} → 4f{sup 7} transition of Eu{sup 2+} was studied in both host systems. Additionally, the {sup 5}D{sub 0} → {sup 7}F{sub J} transition of Eu{sup 3+} was used as an environment probe in the pristine glass and the glass-ceramic.

  7. On the induction of homogeneous bulk crystallization in Eu-doped calcium aluminosilicate glass by applying simultaneous high pressure and temperature

    Science.gov (United States)

    Muniz, R. F.; de Ligny, D.; Le Floch, S.; Martinet, C.; Rohling, J. H.; Medina, A. N.; Sandrini, M.; Andrade, L. H. C.; Lima, S. M.; Baesso, M. L.; Guyot, Y.

    2016-06-01

    From initial calcium aluminosilicate glass, transparent glass-ceramics have been successfully synthesized under simultaneous high pressure and temperature (SHPT). Possible homogeneous volumetric crystallization of this glassy system, which was not achieved previously by means of conventional heat treatment, has been put in evidence with a SHPT procedure. Structural, mechanical, and optical properties of glass and glass-ceramic obtained were investigated. Raman spectroscopy and X-ray diffraction allowed to identify two main crystalline phases: merwinite [Ca3Mg(SiO4)2] and diopside [CaMgSi2O6]. A Raman scanning profile showed that the formation of merwinite is quite homogeneous over the bulk sample. However, the sample surface also contains significant diopside crystals. Instrumented Berkovich nanoindentation was applied to determine the effect of SHPT on hardness from glass to glass-ceramic. For Eu-doped samples, the broadband emission due to 4f65d1 → 4f7 transition of Eu2+ was studied in both host systems. Additionally, the 5D0 → 7FJ transition of Eu3+ was used as an environment probe in the pristine glass and the glass-ceramic.

  8. Wetting of WC by a Zr-base metallic glass-forming alloy

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Ping, E-mail: shenping@jlu.edu.cn [Key Laboratory of Automobile Materials (Ministry of Education), Department of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Zheng, Xiao-Hong [Key Laboratory of Automobile Materials (Ministry of Education), Department of Materials Science and Engineering, Jilin University, Changchun 130025 (China); Liu, Hui-Jie [State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001 (China); Jiang, Qi-Chuan [Key Laboratory of Automobile Materials (Ministry of Education), Department of Materials Science and Engineering, Jilin University, Changchun 130025 (China)

    2013-05-15

    Wetting of hot-pressed polycrystalline WC substrates by a Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} bulk metallic glass (BMG)-forming alloy was investigated at 1133–1253 K in a high vacuum using a modified sessile drop method. The alloy melt spread rapidly on the WC surface, reaching no more than 30° within 3 s, and then slowly (at T < 1213 K) or even remained steady (at T ≥ 1213 K) in the subsequent isothermal dwelling stage. The final equilibrium contact angles were between 11° and 20°, slightly increasing with rising temperature and thus presenting an appreciably anomalous temperature-dependent behavior. The reaction between WC and the Zr-base melt was moderate, slightly enhancing with increasing temperature, and yielded W, ZrC and W{sub 5}Zr{sub 3} at the interface. The wetting, in principle, was driven by the formation of a precursor film in front of the triple line as a result of the adsorption of active atoms (primarily Zr) rather than by the interfacial reaction. From the viewpoint of the wettability and reactivity, WC is a good reinforcement for the preparation of the Zr-base BMG matrix composites. - Highlights: ► WC shows good wettability and moderate reactivity with the Zr{sub 55}Cu{sub 30}Al{sub 10}Ni{sub 5} melt. ► The final wettability exhibits slightly anomalous dependence on temperature. ► The interfacial reaction yields ZrC, W and W{sub 5}Zr{sub 3} phases. ► The primary driving force for the wetting is the formation of the precursor film in front of the triple line.

  9. Glass-Ceramic Waste Forms for Uranium and Plutonium Residues Wastes - 13164

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Martin W.A.; Moricca, Sam A.; Zhang, Yingjie; Day, R. Arthur; Begg, Bruce D. [Australian Nuclear Science and Technology Organisation (ANSTO), New Illawarra Road, Lucas Heights, NSW 2234 (Australia); Scales, Charlie R.; Maddrell, Ewan R. [National Nuclear Laboratory, Sellafield, Seascale, Cumbria, UK, CA20 1PG (United Kingdom); Hobbs, Jeff [Sellafield Limited, Sellafield, Seascale, Cumbria, UK, CA20 1PG (United Kingdom)

    2013-07-01

    A program of work has been undertaken to treat plutonium-residues wastes at Sellafield. These have arisen from past fuel development work and are highly variable in both physical and chemical composition. The principal radiological elements present are U and Pu, with small amounts of Th. The waste packages contain Pu in amounts that are too low to be economically recycled as fuel and too high to be disposed of as lower level Pu contaminated material. NNL and ANSTO have developed full-ceramic and glass-ceramic waste forms in which hot-isostatic pressing is used as the consolidation step to safely immobilize the waste into a form suitable for long-term disposition. We discuss development work on the glass-ceramic developed for impure waste streams, in particular the effect of variations in the waste feed chemistry glass-ceramic. The waste chemistry was categorized into actinides, impurity cations, glass formers and anions. Variations of the relative amounts of these on the properties and chemistry of the waste form were investigated and the waste form was found to be largely unaffected by these changes. This work mainly discusses the initial trials with Th and U. Later trials with larger variations and work with Pu-doped samples further confirmed the flexibility of the glass-ceramic. (authors)

  10. Correlation between liquid structure and glass forming ability in glassy Ag-based binary alloys

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The atomic structures of liquid Ag-based binary alloys have been investigated in the solidification process by means of X-ray diffraction. The results of liquid structure show that there is a break point in the mean nearest neighbor distance r1 and the coordination number Nmin for glass-forming liquid, while the correlation radius rc and the coordination number Nmin display a monotone variational trend above the break point. It means glass-forming liquids have a steady changing in structure above liquidus and more inhomogeneous state at liquidus. We conclude that there is a strong correlation between liquid structure and glass forming ability in Ag-based binary alloys.

  11. Round-robin testing of a reference glass for low-activity waste forms

    Energy Technology Data Exchange (ETDEWEB)

    Ebert, W. L.; Wolf, S. F.

    1999-12-06

    A round robin test program was conducted with a glass that was developed for use as a standard test material for acceptance testing of low-activity waste glasses made with Hanford tank wastes. The glass is referred to as the low-activity test reference material (LRM). The program was conducted to measure the interlaboratory reproducibility of composition analysis and durability test results. Participants were allowed to select the methods used to analyze the glass composition. The durability tests closely followed the Product Consistency Test (PCT) Method A, except that tests were conducted at both 40 and 90 C and that parallel tests with a reference glass were not required. Samples of LRM glass that had been crushed, sieved, and washed to remove fines were provided to participants for tests and analyses. The reproducibility of both the composition and PCT results compare favorably with the results of interlaboratory studies conducted with other glasses. From the perspective of reproducibility of analysis results, this glass is acceptable for use as a composition standard for nonradioactive components of low-activity waste forms present at >0.1 elemental mass % and as a test standard for PCTS at 40 and 90 C. For PCT with LRM glass, the expected test results at the 95% confidence level are as follows: (1) at 40 C: pH = 9.86 {+-} 0.96; [B] = 2.30 {+-} 1.25 mg/L; [Na] = 19.7 {+-} 7.3 mg/L; [Si] = 13.7 {+-} 4.2 mg/L; and (2) at 90 C: pH = 10.92 {+-} 0.43; [B] = 26.7 {+-} 7.2 mg/L; [Na] = 160 {+-} 13 mg/L; [Si] = 82.0 {+-} 12.7 mg/L. These ranges can be used to evaluate the accuracy of PCTS conducted at other laboratories.

  12. STABILIZING GLASS BONDED WASTE FORMS CONTAINING FISSION PRODUCTS SEPARATED FROM SPENT NUCLEAR FUEL

    Energy Technology Data Exchange (ETDEWEB)

    Kenneth J. Bateman; Charles W. Solbrig

    2008-07-01

    A model has been developed to represent the stresses developed when a molten, glass-bonded brittle cylinder (used to store nuclear material) is cooled from high temperature to working temperature. Large diameter solid cylinders are formed by heating glass or glass-bonded mixtures (mixed with nuclear waste) to high temperature (915°C). These cylinders must be cooled as the final step in preparing them for storage. Fast cooling time is desirable for production; however, if cooling is too fast, the cylinder can crack into many pieces. To demonstrate the capability of the model, cooling rate cracking data were obtained on small diameter (7.8 cm diameter) glass-only cylinders. The model and experimental data were combined to determine the critical cooling rate which separates the non-cracking stable glass region from the cracked, non-stable glass regime. Although the data have been obtained so far only on small glass-only cylinders, the data and model were used to extrapolate the critical-cooling rates for large diameter ceramic waste form (CWF) cylinders. The extrapolation estimates long term cooling requirements. While a 52-cm diameter cylinder (EBR-II-waste size) can be cooled to 100°C in 70 hours without cracking, a 181.5-cm diameter cylinder (LWR waste size) requires 35 days to cool to 100°C. These cooling times are long enough that verification of these estimates are required so additional experiments are planned on both glass only and CWF material.

  13. Polymeric microlens array formed directly on glass plate

    Science.gov (United States)

    Zhou, Zuowei; Ren, Hongwen

    2017-01-01

    We prepared a polymeric microlens array (MLA) using ultraviolet (UV) light to cure photosensitive monomers through a photomask. After a short-time UV exposure, the uncured monomers experience a process of partial wetting and self-development on the surface of cured monomers. As a result, a geometric relief with a lens character is generated. Depending on the pattern of the photomask, either a convex or concave MLA can be fabricated. The mechanism of forming the MLA is explained and the concept is proved experimentally. Owing to the merits of simple fabrication, good flexibility, and high optical performance, the MLA has potential applications in light diffusers, fiber/organic light-emitting diode couplers, biomedical imaging, and displays.

  14. The Production of Advanced Glass Ceramic HLW Forms using Cold Crucible Induction Melter

    Energy Technology Data Exchange (ETDEWEB)

    Veronica J Rutledge; Vince Maio

    2013-10-01

    Cold Crucible Induction Melters (CCIMs) will favorably change how High-Level radioactive Waste (from nuclear fuel recovery) is treated in the 21st century. Unlike the existing Joule-Heated Melters (JHMs) currently in operation for the glass-based immobilization of High-Level Waste (HLW), CCIMs offer unique material features that will increase melt temperatures, increase throughput, increase mixing, increase loading in the waste form, lower melter foot prints, eliminate melter corrosion and lower costs. These features not only enhance the technology for producing HLW forms, but also provide advantageous attributes to the waste form by allowing more durable alternatives to glass. This paper discusses advantageous features of the CCIM, with emphasis on features that overcome the historical issues with the JHMs presently utilized, as well as the benefits of glass ceramic waste forms over borosilicate glass waste forms. These advantages are then validated based on recent INL testing to demonstrate a first-of-a-kind formulation of a non-radioactive ceramic-based waste form utilizing a CCIM.

  15. Stability-Indicating TLC-densitometric determination of nebivolol hydrochloride in bulk and pharmaceutical dosage form.

    Science.gov (United States)

    Shirkhedkar, Atul A; Bugdane, Prasad M; Surana, Sanjay J

    2010-02-01

    A simple, selective, precise, and stability-indicating high-performance thin-layer chromatographic (HPTLC) method for densitometric determination of nebivolol hydrochloride both as a bulk drug and in formulation was developed and validated as per the international conference on harmonization guidelines (ICH). The method employed TLC aluminium plates precoated with silica gel 60F254 as the stationary phase. The solvent system consisted of toluene-methanol-triethylamine (3.8:1.2:0.2 v/v/v). Densitometry analysis of nebivolol hydrochloride was carried out in the absorbance mode at 281 nm. The system was found to give compact spot for nebivolol hydrochloride (R(f) value of 0.33 +/- 0.02). The linear regression analysis data for the calibration plots showed good relationship with r(2)= 0.9994 +/- 0.0002 in the concentration range 500-3000 ng/spot. The mean value +/- SD of slope and intercept were 3.761 +/- 0.017 and 127.39 +/- 19.53 with respect to peak area. The limits of detection (LOD) and limit of quantitation (LOQ) were 63.10 ng/spot and 191.23 ng/ spot, respectively. Nebivolol hydrochloride was subjected to acid and alkali hydrolysis, oxidation, thermal degradation, and photodegradation. All the peaks of degradation products were well-resolved from the standard drug with significantly different R(f) values. Statistical analysis proves that the method is repeatable, selective and accurate for the estimation of said drug. The proposed developed HPTLC method can be applied for identification and quantitative determination of nebivolol hydrochloride in the bulk and pharmaceutical dosage form.

  16. Stability-indicating HPTLC determination of imatinib mesylate in bulk drug and pharmaceutical dosage form.

    Science.gov (United States)

    Vadera, N; Subramanian, G; Musmade, P

    2007-01-17

    A simple, selective, precise and stability-indicating high-performance thin-layer chromatographic method of analysis of imatinib mesylate both as a bulk drug and in formulations was developed and validated. The method employed HPTLC aluminium plates precoated with silica gel 60F-254 as the stationary phase. The solvent system consisted of chloroform:methanol (6:4, v/v). The system was found to give compact spot for imatinib mesylate (R(f) value of 0.53+/-0.02). Densitometric analysis of imatinib mesylate was carried out in the absorbance mode at 276 nm. The linear regression analysis data for the calibration plots showed good linear relationship with r(2)=0.9966+/-0.0013 with respect to peak area in the concentration range 100-1000 ng per spot. The mean value+/-S.D. of slope and intercept were 164.85+/-0.72 and 1168.3+/-8.26 with respect to peak area. The method was validated for precision, recovery and robustness. The limits of detection and quantitation were 10 and 30 ng per spot, respectively. Imatinib mesylate was subjected to acid and alkali hydrolysis, oxidation and thermal degradation. The drug undergoes degradation under acidic, basic, oxidation and heat conditions. This indicates that the drug is susceptible to acid, base hydrolysis, oxidation and heat. Statistical analysis proves that the method is repeatable, selective and accurate for the estimation of said drug. The proposed developed HPTLC method can be applied for identification and quantitative determination of imatinib mesylate in bulk drug and dosage forms.

  17. Phenomenological microstructure simulation of incremental bulk metal forming using a multi mesh method

    Science.gov (United States)

    Hirt, G.; Schäfer, D.

    2010-06-01

    For the process design of incremental forming processes like ring rolling or stretch forging there is need for fast and accurate simulation techniques. For many applications it would be necessary to predict the microstructural evolution during the process. For this reason the FEM-software Larstran/Shape which is used for the plastomechanical simulation can be coupled with the microstructure simulation module Strucsim. This software uses phenomenological equations for the calculation of recrystallization (dynamic and static) and grain size evolution [7]. To accelerate the simulation a multi mesh method has been developed. This method uses an adapted simulation mesh with fine elements only in the locally limited contact and forming zone to achieve a reduction of the number of elements. Due to the relative movement of the tool and workpiece the adapted FE-mesh has to be remeshed regularly according to the position of the tool. To avoid loss of information caused by the use of coarse elements the multi mesh method uses a second storage mesh which represents the entire workpiece and which is discretized using only fine elements. For the update of the storage mesh the displacement vectors and changes of scalar values like temperature can be interpolated. For the application of the multi mesh method to the microstructure simulation the update algorithm for the microstructure values has to be modified. The microstructure and plastomechanical simulation have to be uncoupled and the static recrystallization and grain growth outside the forming zone have to be calculated separately. Using the multi mesh method the simulation of incremental bulk metal forming processes including a microstructural simulation can be accelerated. The acceleration factor of the simulation compared to a simulation without adaptive meshing is dependent on the reduction of elements and nodes.

  18. RP-HPLC Method Development and Validation of Abacavir Sulphate in Bulk and Tablet Dosage Form

    Directory of Open Access Journals (Sweden)

    S. LAVANYA

    2014-11-01

    Full Text Available RP-HPLC method was developed for the estimation of abacavir sulphate in bulk and pharmaceutical dosage form (tablets by using INERTSIL ODS 3V column, C18 (250x4.6 ID mobile phase consisting of a mixture of 10mM phosphate buffer: ACN (60:40 v/v % PH: 4.0 with detection of 287 nm. The retention time was found to be 2.430min and linearity was observed in the range 60-140μg /ml. Still now there were a number of analytical methods were developed for the estimation of abacavir in pharmaceutical dosage form and also in biological samples like spectroscopic methods, chromatographic methods, etc. But the present method was met the validation parameters according ICH guidelines like accuracy, precision, linearity, range, robustness, ruggedness, limit of detection and limit of quantitation, etc. with a short around time. The method was found to be precise as indicated by the repeatability analysis, showing %RSD less than 2.

  19. New Simple UV Spectrophotometric Method for Determination of Mirtazapine in Bulk and pharmaceutical dosage forms

    Directory of Open Access Journals (Sweden)

    Sk. Benajeer

    2012-10-01

    Full Text Available Mirtazapine is chemically a tetratetracyclic (pyridodibenzazepine derivative which is classified as a noradrenergic and specific serotonergic antidepressant (NaSSA. Mirtazapine acts as an antagonist at central pre-synaptic α2-receptors, inhibiting negative feedback to the presynaptic nerve and causing an increase in NErelease. It is also used for the treatment of Posttraumatic stress disorder. In present work, simple, sensitive, accurate and economical spectroscopic method has been developed for the estimation of mirtazapine in bulk and its pharmaceutical dosage forms. An absorption maximum was found to be at 232nm with the solvent systemphosphate buffer (pH 6.8. The drug follows beer’s law in the range of 5-30μg/ml with correlation coefficient of 0.999. The percentage recovery of mirtazapine ranged from 99.57-100.26% in pharmaceutical dosage form. Results of the analysis were validated for accuracy, precision, LOD, LOQ and were found to be satisfactory. The proposed method is simple, rapid and suitable for the routine quality control analysis.

  20. Is Cu60Ti10Zr30 a bulk glass-forming alloy?

    DEFF Research Database (Denmark)

    Jiang, Jianzhong; Saida, J.; Kato, H.

    2003-01-01

    . Nanocrystals with a significant volume fraction are randomly distributed in the amorphous matrix. The copper element is enriched in nanocrystals while a slightly high zirconium content is found in the matrix. We classify that the Cu60Ti10Zr30 alloy prepared by both of the aforementioned methods...

  1. Role of fivefold symmetry in the dynamical slowing down of metallic glass-forming liquids

    Science.gov (United States)

    Lü, Y. J.; Bi, Q. L.; Huang, H. S.; Pang, H. H.

    2017-08-01

    Fivefold symmetry is supposed to have an important role in suppressing crystallization and promoting glass transition due to its structural incompatibility with crystal. In this paper, we study the correlation between the fivefold symmetry and the dynamical slowing down in glass-forming Cu-Zr liquids using the single-particle dynamics method based on molecular dynamics simulations. The dynamics of the glass-forming liquids is microscopically characterized by the jump cage motion for individual atoms; moreover, the cooperative jumps become more pronounced upon approaching the glass transition temperature. We find that the role of fivefold symmetry in the dynamical slowing down does not lie in caging atomic motion but, more importantly, in suppressing cooperative jumps. The atoms with a high degree of fivefold symmetry and involved in jump motions appear more sluggish compared to other jumps. This behavior significantly suppresses the cooperative jumps around them, leading to the slowing down of fast dynamics. The degree of suppression has a close relation to the glass-forming ability and contributes to the "strong" character of liquids.

  2. Glass composite waste forms for iodine confined in bismuth-embedded SBA-15

    Science.gov (United States)

    Yang, Jae Hwan; Park, Hwan Seo; Ahn, Do-Hee; Yim, Man-Sung

    2016-11-01

    The aim of this study was to stabilize bismuth-embedded SBA-15 that captured iodine gas by fabrication of monolithic waste forms. The iodine containing waste was mixed with Bi2O3 (a stabilizing additive) and low-temperature sintering glass followed by pelletizing and the sintering process to produce glass composite materials. Iodine volatility during the sintering process was significantly affected by the ratio of Bi2O3 and the glass composition. It was confirmed that BiI3, the main iodine phase within bismuth-embedded SBA-15, was effectively transformed to the mixed phases of Bi5O7I and BiOI. The initial leaching rates of iodine from the glass composite waste forms ranged 10-3-10-2 g/m2 day, showing the stability of the iodine phases encapsulated by the glassy networks. It was also observed that common groundwater anions (e.g., chloride, carbonate, sulfite, and fluoride) elevated the iodine leaching rate by anion exchange reactions. The present results suggest that the glass composite waste form of bismuth-embedded SBA-15 could be a candidate material for stable storage of 129I.

  3. Specimen Size Effects on Zr-Based Bulk Metallic Glasses Investigated by Uniaxial Compression and Spherical Nanoindentation

    Science.gov (United States)

    Bei, H.; Lu, Z. P.; Shim, S.; Chen, G.; George, E. P.

    2010-07-01

    Specimen size effects on the mechanical behavior of Zr-based bulk metallic glasses (BMGs) were investigated by compression and nanoindentation tests. In compression, even at the 1- to 10-mm scale, stable shear band propagation and extensive plastic deformation can be achieved in small (2 mm) specimens, in contrast to large (6.5 mm) specimens, which fail catastrophically after limited plastic deformation. The yield strength is independent of specimen size in this range, and plastic deformation remains highly localized in a few shear bands even in those specimens that exhibit stable shear sliding. The fracture surfaces of small specimens are smooth, without the vein patterns normally observed as characteristic features on the fracture surfaces of BMGs. During spherical nanoindentation, it is found that the upper bound of the maximum shear stress to initiate plasticity (yielding) in a Zr-based BMG is almost constant for indenter radii smaller than ~90 µm. However, the lower bound of this maximum shear stress decreases with increasing indenter radius, probably due to the increased probability of finding defects underneath larger indenters.

  4. THE EFFECTS OF GAMMA-RAY ON THE MECHANICAL PROPERTIES OF Zr-BASED BULK METALLIC GLASS

    Directory of Open Access Journals (Sweden)

    L. H. Shah

    2012-12-01

    Full Text Available The effect of gamma-ray irradiation on the mechanical properties of Zr55Ni5Al10Cu30 bulk metallic glass (BMG was investigated. The samples were irradiated with a gamma-ray dose up to 2090.24 kGy prior to mechanical property investigations. Vickers hardness test, nano-indentation test as well as speed of sound measurements in order to calculate the material’s elastic moduli were conducted. An x-ray diffractogram device was also utilized to observe the BMG’s devitrification behavior. Results confirm that no significant changes were observed for any of the samples. XRD spectra of irradiated BMGs also show uniform broad peaks, indicating an amorphous structure inside the sample. This result indicates that a gamma-ray irradiation dose of up to 2090.24 kGy does not change the mechanical properties and the microstructure of the material, thus making it a good future structural candidate for gamma-ray rich environments.

  5. Comparative study of bulk metallic glass composites with high-volume-fractioned dendritic and spherical b. c. c. phase precipitates

    Directory of Open Access Journals (Sweden)

    Guo-yuan Sun

    2015-05-01

    Full Text Available A dendritic β-phase reinforced bulk metallic glass (BMG composite named as D2 was prepared by rapid quenching of a homogenous Zr60Ti14.67Nb5.33Cu5.56Ni4.44Be10 melt, and characterized by means of X-ray diffraction (XRD, scanning electron microscopy (SEM observation and room-temperature compression test. The microstructure and mechanical properties were compared with those of the spherical β-phase reinforced composite named as composite S2. It was found that the composite D2 contains β-phase dendrites up to 56% in volume-fraction, and exhibits a ductile compressive behavior with plastic strain of 12.7%. As the high-volume-fractioned β-phase dendrites transferred to coarse spherical particles of about 20 μm in diameter in the composite S2, a much improved plastic strain up to 20.4% can be achieved. Micrographs of the fractured samples reveal different interaction modes of the propagating shear bands with the dendritic and spherical β phase inclusions, resulting in different shear strains in the composite samples. The matrix of composite S2 undergoes a significantly larger shear strain than that of the composite D2 before ultimate failure, which is thought to be mainly responsible for the greatly increased global plastic strain of the S2 relative to D2.

  6. Effect of Annealing Treatment on Erosion-Corrosion of Zr-Based Bulk Metallic Glass in Saline-Sand Slurry

    Science.gov (United States)

    Ji, Xiulin; Shan, Yiping; Chen, Yueyue; Wang, Hui

    2016-06-01

    Bulk metallic glass (BMG) may be a good candidate to solve the erosion-corrosion (E-C) problems of marine pumps in sand-containing seawater. Since annealing treatment is an effective way to improve plasticity of BMGs, the effect of annealing treatment on E-C wear of Zr-based BMG in saline-sand slurry was investigated. All of the annealed BMG samples were crystallized and the quantity of (Zr, Cu) phase increased but that of Al4Cu9 phase decreased with the increase of annealing temperature from 360 to 480 °C. Accordingly, annealing treatment enhances plasticity of the as-cast BMG at the cost of hardness and corrosion resistance. Moreover, 480 °C annealed BMG sample possesses the highest hardness and the lowest corrosion current density in all of the annealed BMG samples. Using a slurry pot erosion tester, the E-C wear of the as-cast and annealed BMG samples was studied under different impingement angles, impact velocities, and concentrations in saline-sand slurry. With the improvement of plasticity, 480 °C annealed BMG sample exhibits the best E-C wear resistance under high impingement angle, high impact velocity, and high sand concentration.

  7. Relation between icosahedral short-range ordering and plastic deformation in Zr-Nb-Cu-Ni-Al bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Z.W. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Gu, L. [WPI, Advance Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Xie, G.Q. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Zhang, W., E-mail: wzhang@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Inoue, A. [WPI, Advance Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Zhang, H.F., E-mail: hfzhang@imr.ac.cn [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Hu, Z.Q. [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2011-04-15

    The relation between icosahedral short-range ordering (ISRO) and plastic deformation was investigated in Zr{sub 70-x}Nb{sub x}Cu{sub 13.5}Ni{sub 8.5}Al{sub 8} (at.%, x = 0, 2, 4, 6, 7, 8, 10) bulk metallic glasses (BMG). The formation of icosahedral quasicrystal (I-phase) during the annealing process implies that ISRO widely exists in these materials. The degree of ISRO is thermodynamically evaluated to show that ISRO increases with increasing Nb content. Compression tests indicate that BMG with 0-7 at.% Nb possess similar unusual plastic deformability, which is attributed to ISRO-mediated local distribution of free volume (FV) and ISRO prompted deformation-induced crystallization. A proposed core-shell model coupled with transmission electron microscopy analysis demonstrates that the FV is distributed more heterogeneously with increasing ISRO, which is beneficial for multiplying the shear bands. Deformation-induced crystallization is facilitated, owing to the low interfacial energy of the nucleation and growth of the crystals attributed to ISRO in the amorphous matrix, which improves plasticity by consuming energy and the product altering the stress field in the amorphous matrix. Design of new ductile BMG is discussed in these strategies.

  8. Studies of Shear Band Velocity Using Spatially and Temporally Resolved Measurements of Strain During Quasistatic Compression of Bulk Metallic Glass

    Energy Technology Data Exchange (ETDEWEB)

    Wright, W J; Samale, M; Hufnagel, T; LeBlanc, M; Florando, J

    2009-06-15

    We have made measurements of the temporal and spatial features of the evolution of strain during the serrated flow of Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass tested under quasistatic, room temperature, uniaxial compression. Strain and load data were acquired at rates of up to 400 kHz using strain gages affixed to all four sides of the specimen and a piezoelectric load cell located near the specimen. Calculation of the displacement rate requires an assumption about the nature of the shear displacement. If one assumes that the entire shear plane displaces simultaneously, the displacement rate is approximately 0.002 m/s. If instead one assumes that the displacement occurs as a localized propagating front, the velocity of the front is approximately 2.8 m/s. In either case, the velocity is orders of magnitude less than the shear wave speed ({approx}2000 m/s). The significance of these measurements for estimates of heating in shear bands is discussed.

  9. Corrosion-fatigue study of a Zr-based bulk-metallic glass in a physiologically relevant environment

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Lu [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, XueYuan Road No. 37, HaiDian District, Beijing 100191 (China); Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996-2200 (United States); Wang, Gongyao; Qiao, Dongchun; Liaw, Peter K. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN 37996-2200 (United States); Pang, Shujie; Wang, Jianfeng [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, XueYuan Road No. 37, HaiDian District, Beijing 100191 (China); Zhang, Tao, E-mail: zhangtao@buaa.edu.c [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beijing University of Aeronautics and Astronautics, XueYuan Road No. 37, HaiDian District, Beijing 100191 (China)

    2010-08-15

    Four-point-bend corrosion-fatigue experiments were conducted in a physiologically relevant environment to study the environmental effects on the fatigue behavior of (Zr{sub 0.55}Al{sub 0.10}Ni{sub 0.05}Cu{sub 0.30}){sub 99}Y{sub 1} (at.%) bulk-metallic glasses (BMGs), and the results were compared with those obtained in air at room temperature. At high stress ranges, the corrosive environment did not significantly affect the fatigue lifetime; while at low stress ranges, the corrosive environment exhibited a detrimental effect on the fatigue resistance. The fatigue strength was decreased by 40% in the physiologically relevant environment. Fracture morphologies after fatigue tests were studied by the scanning electron microscopy. The mechanism for the environmental effects on the fatigue life of the (Zr{sub 0.55}Al{sub 0.10}Ni{sub 0.05}Cu{sub 0.30}){sub 99}Y{sub 1} BMG was determined to be anodic dissolution.

  10. Analysis of the Influence of Element's Entropy on the Bulk Metallic Glass (BMG) Entropy, Complexity, and Strength

    Science.gov (United States)

    Namazi, Hamidreza; Akrami, Amin; Haghighi, Reza; Delaviz, Ali; Kulish, Vladimir V.

    2017-02-01

    Bulk metallic glasses (BMGs) are disordered compounds without a long-range crystalline order. In this paper, we study the effect of an element's standard entropy on the BMG's entropy and complexity for four elements. In order to do this, we simulate the BMG structures first. Then we compute the entropy and fractal dimension of the resulting structures as measures of disorder and complexity, respectively. We verify our predictions via experiments. In doing so, we substitute the elements in separate experiments and compute the fractal dimension of the obtained BMG pattern. The results of our investigations show that there is a relation between the variations of elements' entropies and the variations of BMGs' entropy and fractality. On the other hand, measurement of the compressive strength for the obtained BMGs from experiments shows that by increasing the entropy and fractal dimension, BMG's compressive strength increases. The adaptive capability observed in this method could potentially be harnessed for targeted BMG production, depending on the specific design goal. The method discussed here is not only useful for analysis of BMG structures, but it can be applied to other structures.

  11. Understanding the glass-forming ability of active pharmaceutical ingredients for designing supersaturating dosage forms.

    Science.gov (United States)

    Kawakami, Kohsaku; Usui, Toshinori; Hattori, Mitsunari

    2012-09-01

    Amorphous solid dispersions have great potential for enhancing oral absorption of poorly soluble drugs. Crystallization behavior during storage and after exposure to aqueous media must be examined in detail for designing stable and effective amorphous formulations, and it is significantly affected by the intrinsic properties of an amorphous drug. Many attempts have been made to correlate various thermodynamic parameters of pharmaceutical glasses with their crystallization behavior; however, variations in model drugs that could be used for such investigation has been limited because the amorphous characteristics of drugs possessing a high crystallization tendency are difficult to evaluate. In this study, high-speed differential scanning calorimetry, which could inhibit their crystallization using high cooling rates up to 2000°C/s, was employed for assessing such drugs. The thermodynamic parameters of the glasses, including glass transition temperature (T(g)) and fragility, were obtained to show that their crystallization tendency cannot be explained simply by the parameters, although there have been general thought that fragility may be correlated with crystallization tendency. Also investigated was correlation between the thermodynamic parameters and crystallization tendency upon contact with water, which influences in vivo efficacy of amorphous formulations. T(g) was correlated well with the crystallization tendency upon contact with water.

  12. Optimal forming zone length in continuous extrusion of lead-clad glass fiber wire

    Institute of Scientific and Technical Information of China (English)

    李霞; 唐景林; 王丽薇; 高明

    2008-01-01

    Forming zone length (FZL) is a key parameter of the lead-clad glass fiber extrusion dies, and an unsuitable FZL will lead to breakage of the glass fiber and/or unacceptable geometric and metallographic qualities of the product. The optimal FZL was determined theoretically based on a mathematical model established by upper bound method, and accepted Pb-GF wire was actually obtained experimentally by symmetric side-feed extrusion at a much lower temperature than that published before. The wire has features of fine grains, uniform diameter, good coaxiality and satisfied mechanical property. The results and conclusions obtained in the research can be used to design the forming tools for lead-clad glass fiber extrusion and have significance to further research on the extrusion of other complex wires of metal-clad brittle core.

  13. Cold crucible induction melter studies for making glass ceramic waste forms: A feasibility assessment

    Science.gov (United States)

    Crum, Jarrod; Maio, Vince; McCloy, John; Scott, Clark; Riley, Brian; Benefiel, Brad; Vienna, John; Archibald, Kip; Rodriguez, Carmen; Rutledge, Veronica; Zhu, Zihua; Ryan, Joe; Olszta, Matthew

    2014-01-01

    Glass ceramics are being developed to immobilize fission products, separated from used nuclear fuel by aqueous reprocessing, into a stable waste form suitable for disposal in a geological repository. This work documents the glass ceramic formulation at bench scale and for a scaled melter test performed in a pilot-scale (∼1/4 scale) cold crucible induction melter (CCIM). Melt viscosity, electrical conductivity, and crystallization behavior upon cooling were measured on a small set of compositions to select a formulation for melter testing. Property measurements also identified a temperature range for melter operation and cooling profiles necessary to crystallize the targeted phases in the waste form. Bench scale and melter run results successfully demonstrate the processability of the glass ceramic using the CCIM melter technology.

  14. COLORIMETRIC DETERMINATION OF CEFQUINOME SULPHATE IN BULK AND DOSAGE FORM USING AMMONIUM MOLYBDATE

    Directory of Open Access Journals (Sweden)

    Shaza Wageialla Shantier

    2014-01-01

    Full Text Available This study was designed to develop two colorimetric methods for the determination of Cefquinome Sulphate (CS in bulk and dosage forms using two different concentrations of molybdenum solution. The developed methods were based on the oxidation of CS with 2% ammonium molybdate, in the presence of sulphuric acid, producing a green colored product with λmax at 409 nm (Method I and the oxidation of CS with 10% ammonium molybdate in acidic media to produce a blue colored product with λmax at 673 nm (Method II. The factors affecting the color development and stability were optimized and incorporated in the procedure. Beer’s law was obeyed over the concentration range 16-80 µg mL-1 (Method I and 40-80 µg mL-1 (Method II with a correlation coefficient not less than 0.999. The limit of detection and limit of quantification were 5.7 and 18.9 µg mL-1 for Method I, 4.25 µg mL-1 and 14.2 µg mL-1 for Method II respectively. The average recovery for the dosage form (suspension 2.5% was 100.30% ±0.59; n = 3, which reflected no interference by the suspension excipients. The results obtained by the developed methods for the suspension dosage form were statistically compared with those of a developed HPLC method and evaluated at 95% confidence limits. The developed methods were proved to be accurate and simple. The methods involved in the study covered, Colorimetric spectrophotometry, High Performance Liquid Chromatography. The molar ratio method is recommended to be conducted in order to determine the reaction stoichiometry.

  15. Apatite forming ability and cytocompatibility of pure and Zn-doped bioactive glasses.

    Science.gov (United States)

    Oudadesse, H; Dietrich, E; Gal, Y L; Pellen, P; Bureau, B; Mostafa, A A; Cathelineau, G

    2011-06-01

    The use of bone grafts permits the filling of a bone defect without risk of virus transmission. In this work, pure bioactive glass (46S6) and zinc-doped bioactive glass (46S6Zn10) with 0.1 wt% zinc are used to elaborate highly bioactive materials by melting and rapid quenching. Cylinders of both types of glasses were soaked in a simulated body fluid (SBF) solution with the aim of determining the effect of zinc addition as a trace element on the chemical reactivity and bioactivity of glass. Several physico-chemical characterization methods such as x-ray diffraction, Fourier transform infrared spectroscopy and nuclear magnetic resonance methods, with particular focus on the latter, were chosen to investigate the fine structural behaviour of pure and Zn-doped bioactive glasses as a function of the soaking time of immersion in SBF. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to measure the concentrations of Ca and P ions in the SBF solution after different durations of immersion. The effect of the investigated samples on the proliferation rate of human osteoblast cells was assessed by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, and tested on two different sizes of pure and zinc-doped glasses in powder form, with particle sizes that ranged between 40 to 63 µm and 500 to 600 µm. The obtained results showed the delay release of ions by Zn-doped glass (46S6Zn10) and the slower CaP deposition. Cytotoxicity and cell viability were affected by the particle size of the glass. The release rate of ions was found to influence the cell viability.

  16. Preparation of Carbon-nanotube Reinforced Mg Based Bulk Metallic Glass Composites and Its Mechanical Properties%碳纳米管—镁基非晶复合材料的制备及力学性能

    Institute of Scientific and Technical Information of China (English)

    赵平; 李双寿; 彭浩; 刘金海

    2011-01-01

    Carbon-nanotube reinforced Mg-based bulk metallic glass composites were prepared successfully with copper mold by differential pressure casting. Moreover, the microstructure, compressive behavior, fracture strength as well as fracture morphology of the composites were investigated. The results show that there exists desirable bonding between carbon-nanotube particle and the Mg-based bulk metallic glass, and the glass forming ability and thermal stability of the Mg-based bulk metallic glass can not be apparently changed by the induction of carbon-nanotube particle. Compared with the matrix a-morphous alloy, the composites exhibit obvious advantages in the maximum compressive strength and fracture displacement. Carbon-nanotube is uniformly distributed into the matrix amorphous alloy in the absence of large-area colony, meanwhile, amounts of dimple structure in the fracture morphology of the composites can be observed.%采用铜模差压压铸的方法成功制备了碳纳米管颗粒增强镁基非晶复合材料,并对其微观结构、压缩性能、断裂强度及断口形貌进行了研究.结果表明,碳纳米管颗粒与非晶基体结合良好,其引入没有明显改变基体非晶合金的玻璃形成能力和热稳定性能;与非晶合金相比,复合材料的最大压缩强度及断裂位移有明显提高.碳纳米管在基体中复合的比较均匀,没有出现大面积团聚,并形成很多韧窝结构.

  17. Radiation stability test on multiphase glass ceramic and crystalline ceramic waste forms

    Science.gov (United States)

    Tang, Ming; Kossoy, Anna; Jarvinen, Gordon; Crum, Jarrod; Turo, Laura; Riley, Brian; Brinkman, Kyle; Fox, Kevin; Amoroso, Jake; Marra, James

    2014-05-01

    A radiation stability study was performed on glass ceramic and crystalline ceramic waste forms. These materials are candidate host materials for immobilizing alkali/alkaline earth (Cs/Sr-CS) + lanthanide (LN) + transition metal (TM) fission product waste streams from nuclear fuel reprocessing. In this study, glass ceramics were fabricated using a borosilicate glass as a matrix in which to incorporate CS/LN/TM combined waste streams. The major phases in these multiphase materials are powellite, oxyaptite, pollucite, celsian, and durable residual glass phases. Al2O3 and TiO2 were combined with these waste components to produce multiphase crystalline ceramics containing hollandite-type phases, perovskites, pyrochlores and other minor metal titanate phases. For the radiation stability test, selected glass ceramic and crystalline ceramic samples were exposed to different irradiation environments including low fluxes of high-energy (∼1-5 MeV) protons and alpha particles generated by an ion accelerator, high fluxes of low-energy (hundreds of keV) krypton particles generated by an ion implanter, and in-situ electron irradiations in a transmission electron microscope. These irradiation experiments were performed to simulate self-radiation effects in a waste form. Ion irradiation-induced microstructural modifications were examined using X-ray diffraction and transmission electron microscopy. Our preliminary results reveal different radiation tolerance in different crystalline phases under various radiation damage environments. However, their stability may be rate dependent which may limit the waste loading that can be achieved.

  18. Atomic structure of Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} bulk metallic glass alloy

    Energy Technology Data Exchange (ETDEWEB)

    Hui, X. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)], E-mail: huixd01@hotmail.com; Fang, H.Z.; Chen, G.L. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Shang, S.L.; Wang, Y. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Qin, J.Y. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University - Southern Campus, Jinan 250061 (China); Liu, Z.K. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA 16802 (United States)

    2009-01-15

    Ab initio molecular dynamics (AIMD) calculations were performed on the atomic configuration of Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5} bulk metallic glass. The local structures were characterized in terms of structure factors (SF), pair correlation functions (PCF), coordinate numbers, bond pairs and Voronoi polyhedra. The glass transition temperature, generalized PCF and SF predicated by AIMD are in good agreement with the experimental data. Icosahedral short-range orders (ISRO) are found to be the most dominant, in view of the presence of the majority of bond pairs with 1551, 1541 and 1431, and Voronoi polyhedra with <0,3,6,1>, <0,2,8,1>, <0,0,12,0> and <0,2,8,4>. Icosahedral medium range orders (IMROs) are formed from icosahedra via the linkage of vertex-, edge-, face- and intercross-shared atoms. The glass structure on the nanometer scale is accumulated by polyhedra through an efficient packing mode. It is suggested that the extraordinary glass-forming ability of this alloy is essentially attributable to the formation of ISRO and IMRO, and the dense packing of atoms.

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

    NARCIS (Netherlands)

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

    2009-01-01

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

  20. Glass-Forming Tendency of Molecular Liquids and the Strength of the Intermolecular Attractions

    Science.gov (United States)

    Koperwas, Kajetan; Adrjanowicz, Karolina; Wojnarowska, Zaneta; Jedrzejowska, Agnieszka; Knapik, Justyna; Paluch, Marian

    2016-11-01

    When we cool down a liquid below the melting temperature, it can either crystallize or become supercooled, and then form a disordered solid called glass. Understanding what makes a liquid to crystallize readily in one case and form a stable glass in another is a fundamental problem in science and technology. Here we show that the crystallization/glass-forming tendencies of the molecular liquids might be correlated with the strength of the intermolecular attractions, as determined from the combined experimental and computer simulation studies. We use van der Waals bonded propylene carbonate and its less polar structural analog 3-methyl-cyclopentanone to show that the enhancement of the dipole-dipole forces brings about the better glass-forming ability of the sample when cooling from the melt. Our finding was rationalized by the mismatch between the optimal temperature range for the nucleation and crystal growth, as obtained for a modeled Lennard-Jones system with explicitly enhanced or weakened attractive part of the intermolecular 6-12 potential.

  1. Crossover to potential energy landscape dominated dynamics in a model glass-forming liquid

    DEFF Research Database (Denmark)

    Schrøder, Thomas; Sastry, S.; Dyre, Jeppe;

    2000-01-01

    An equilibrated model glass-forming liquid is studied by mapping successive configurations produced by molecular dynamics simulation onto a time series of inherent structures (local minima in the potential energy). Using this "inherent dynamics" approach we find direct numerical evidence for the ...

  2. Exploring the Origin of Fragile-to-Strong Transition in Some Glass-Forming Liquids

    DEFF Research Database (Denmark)

    Yue, Yuanzheng; Hu, L. N.

    2014-01-01

    The slow dynamics of glass-forming liquids is a complex subject of the condensed matter science. But the fragile-to-strong transition, which was observed not long ago [Ito, et al, Nature 1999], makes this subject even more complex since it is extremely challenging to directly probe the structural...

  3. On the possible existence of crystallites in glass-forming liquids

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    We speculate that glass-forming liquids may contain fairly large and well-defined crystallites. This is based on arguing that the slowly relaxing "frozen-in" stresses characterizing ultraviscous liquids increase the barrier for nucleation, thus allowing for larger unstable crystallites than other...

  4. Thermal forming of glass microsheets for x-ray telescope mirror segments

    DEFF Research Database (Denmark)

    Jimenez-Garate, M.A.; Hailey, C.J.; Craig, W.W.

    2003-01-01

    We describe a technology to mass-produce ultrathin mirror substrates for x-ray telescopes of near Wolter-I geometry. Thermal glass forming is a low-cost method to produce high-throughput, spaceborne x-ray mirrors for the 0.1-200-keV energy band. These substrates can provide the collecting area...

  5. The effect of Nb addition on mechanical properties, corrosion behavior, and metal-ion release of ZrAlCuNi bulk metallic glasses in artificial body fluid.

    Science.gov (United States)

    Qiu, C L; Liu, L; Sun, M; Zhang, S M

    2005-12-15

    Bulk metallic glasses (BMGs) of Zr(65 - x)Nb(x)- Cu(17.5)Ni(10)Al(7.5) with Nb = 0, 2, and 5 at % were prepared by copper mold casting. Compression tests reveal that the two BMGs containing Nb exhibited superior strength and plasticity to the base alloy. The corrosion behavior of the alloys obtained was investigated in artificial body fluid by electrochemical measurements. It was found that the addition of Nb significantly enhanced the corrosion resistance of the Zr-based BMG, as indicated by a remarkable increase in corrosion potential and pitting potential. XPS analysis revealed that the passive film formed after anodic polarization was enriched in aluminum oxide and depleted in phosphate ions for the BMGs containing Nb, which accounts for the improvement of corrosion resistance. On the other hand, metal-ion release of different BMGs were determined in PPb (ng/mL) level with inductively coupled plasma mass spectrometry (ICP-MS) after being immersed in artificial body fluid at 37 degrees C for 20 days. It was found that the addition of Nb considerably reduced the ion release of all kinds of metals of the base system. This is probably attributed to the promoting effect of Nb on a rapid formation of highly protective film.

  6. Composition dependence of the glass forming ability in binary mixtures: The role of demixing entropy

    Science.gov (United States)

    Nandi, Ujjwal Kumar; Banerjee, Atreyee; Chakrabarty, Suman; Bhattacharyya, Sarika Maitra

    2016-07-01

    We present a comparative study of the glass forming ability of binary systems with varying composition, where the systems have similar global crystalline structure (CsCl+fcc). Biased Monte Carlo simulations using umbrella sampling technique show that the free energy cost to create a CsCl nucleus increases as the composition of the smaller particles is decreased. We find that systems with comparatively lower free energy cost to form CsCl nucleus exhibit more pronounced pre-crystalline demixing near the liquid/crystal interface. The structural frustration between the CsCl and fcc crystal demands this demixing. We show that closer to the equimolar mixture, the entropic penalty for demixing is lower and a glass forming system may crystallize when seeded with a nucleus. This entropic penalty as a function of composition shows a non-monotonic behaviour with a maximum at a composition similar to the well known Kob-Anderson (KA) model. Although the KA model shows the maximum entropic penalty and thus maximum frustration against CsCl formation, it also shows a strong tendency towards crystallization into fcc lattice of the larger "A" particles which can be explained from the study of the energetics. Thus for systems closer to the equimolar mixture although it is the requirement of demixing which provides their stability against crystallization, for KA model it is not demixing but slow dynamics and the presence of the "B" particles make it a good glass former. The locally favoured structure around "B" particles is quite similar to the CsCl structure and the incompatibility of CsCl and fcc hinders the fcc structure growth in the KA model. Although the glass forming binary systems studied here are quite similar, differing only in composition, we find that their glass forming ability cannot be attributed to a single phenomenon.

  7. Composition dependence of the glass forming ability in binary mixtures: The role of demixing entropy.

    Science.gov (United States)

    Nandi, Ujjwal Kumar; Banerjee, Atreyee; Chakrabarty, Suman; Bhattacharyya, Sarika Maitra

    2016-07-21

    We present a comparative study of the glass forming ability of binary systems with varying composition, where the systems have similar global crystalline structure (CsCl+fcc). Biased Monte Carlo simulations using umbrella sampling technique show that the free energy cost to create a CsCl nucleus increases as the composition of the smaller particles is decreased. We find that systems with comparatively lower free energy cost to form CsCl nucleus exhibit more pronounced pre-crystalline demixing near the liquid/crystal interface. The structural frustration between the CsCl and fcc crystal demands this demixing. We show that closer to the equimolar mixture, the entropic penalty for demixing is lower and a glass forming system may crystallize when seeded with a nucleus. This entropic penalty as a function of composition shows a non-monotonic behaviour with a maximum at a composition similar to the well known Kob-Anderson (KA) model. Although the KA model shows the maximum entropic penalty and thus maximum frustration against CsCl formation, it also shows a strong tendency towards crystallization into fcc lattice of the larger "A" particles which can be explained from the study of the energetics. Thus for systems closer to the equimolar mixture although it is the requirement of demixing which provides their stability against crystallization, for KA model it is not demixing but slow dynamics and the presence of the "B" particles make it a good glass former. The locally favoured structure around "B" particles is quite similar to the CsCl structure and the incompatibility of CsCl and fcc hinders the fcc structure growth in the KA model. Although the glass forming binary systems studied here are quite similar, differing only in composition, we find that their glass forming ability cannot be attributed to a single phenomenon.

  8. Evidence for a Disordered Critical Point in a Glass-Forming Liquid.

    Science.gov (United States)

    Berthier, Ludovic; Jack, Robert L

    2015-05-22

    Using computer simulations of an atomistic glass-forming liquid, we investigate the fluctuations of the overlap between a fluid configuration and a quenched reference system. We find that large fluctuations of the overlap develop as temperature decreases, consistent with the existence of the random critical point that is predicted by effective field theories. We discuss the scaling of fluctuations near the presumed critical point, comparing the observed behavior with that of the random-field Ising model. We argue that this critical point directly reveals the existence of an interfacial tension between amorphous metastable states, a quantity relevant both for equilibrium relaxation and for nonequilibrium melting of stable glass configurations.

  9. Single-exponential activation behavior behind the super-Arrhenius relaxations in glass-forming liquids.

    Science.gov (United States)

    Wang, Lianwen; Li, Jiangong; Fecht, Hans-Jörg

    2010-11-17

    The reported relaxation time for several typical glass-forming liquids was analyzed by using a kinetic model for liquids which invoked a new kind of atomic cooperativity--thermodynamic cooperativity. The broadly studied 'cooperative length' was recognized as the kinetic cooperativity. Both cooperativities were conveniently quantified from the measured relaxation data. A single-exponential activation behavior was uncovered behind the super-Arrhenius relaxations for the liquids investigated. Hence the mesostructure of these liquids and the atomic mechanism of the glass transition became clearer.

  10. Mapping strain fields induced in Zr-based bulk metallic glasses during in-situ nanoindentation by X-ray nanodiffraction

    Energy Technology Data Exchange (ETDEWEB)

    Gamcová, J.; Bednarčík, J.; Franz, H. [DESY, Notkestraße 85, Hamburg 22547 (Germany); Mohanty, G.; Wehrs, J.; Michler, J. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkerstraße 39, Thun 3602 (Switzerland); Michalik, Š. [Institute of Physics ASCR, Na Slovance 2, Praha 18221 (Czech Republic); Krywka, C. [HZG, Institut für Werkstoffforschung, Notkestraße 85, Hamburg 22547 (Germany); Breguet, J. M. [Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Mechanics of Materials and Nanostructures, Feuerwerkerstraße 39, Thun 3602 (Switzerland); Alemnis GmbH, Feuerwerkerstraße 39, Thun 3602 (Switzerland)

    2016-01-18

    A pioneer in-situ synchrotron X-ray nanodiffraction approach for characterization and visualization of strain fields induced by nanoindentation in amorphous materials is introduced. In-situ nanoindentation experiments were performed in transmission mode using a monochromatic and highly focused sub-micron X-ray beam on 40 μm thick Zr-based bulk metallic glass under two loading conditions. Spatially resolved X-ray diffraction scans in the deformed volume of Zr-based bulk metallic glass covering an area of 40 × 40 μm{sup 2} beneath the pyramidal indenter revealed two-dimensional map of elastic strains. The largest value of compressive elastic strain calculated from diffraction data at 1 N load was −0.65%. The region of high elastic compressive strains (<−0.3%) is located beneath the indenter tip and has radius of 7 μm.

  11. Formation of quasicrystals in Zr46.8Ti8.2Cu7.5Ni10Be27.5 bulk glass

    DEFF Research Database (Denmark)

    Wanderka, N.; Macht, M. P.; Siedel, M.;

    2000-01-01

    The formation of the quasicrystalline phase is observed as a first step of crystallization during isothermal annealing of the Zr46.7Ti8.3Cu7.5Ni10Be27.5 bulk glass. The structure of the quasicrystals and the sequence of phase formation have been investigated by x-ray powder diffraction and transm......The formation of the quasicrystalline phase is observed as a first step of crystallization during isothermal annealing of the Zr46.7Ti8.3Cu7.5Ni10Be27.5 bulk glass. The structure of the quasicrystals and the sequence of phase formation have been investigated by x-ray powder diffraction...

  12. Evaluation of Ni-free Zr–Cu–Fe–Al bulk metallic glass for biomedical implant applications

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Ying-Sui [Institute of Oral Biology, National Yang-Ming University, Taipei, Taiwan (China); Zhang, Wei [School of Materials Science and Engineering, Dalian University of Technology, Dalian (China); Kai, Wu [Institute of Materials Engineering, National Taiwan Ocean University, Keelung, Taiwan (China); Liaw, Peter K. [Department of Materials Science and Engineering, The University of Tennessee, Knoxville, TN (United States); Huang, Her-Hsiung, E-mail: hhhuang@ym.edu.tw [Institute of Oral Biology, National Yang-Ming University, Taipei, Taiwan (China); Department of Dentistry, National Yang-Ming University, Taipei, Taiwan (China); Department of Dentistry, Taipei City Hospital, Taipei, Taiwan (China); Department of Stomatology, Taipei Veterans General Hospital, Taipei, Taiwan (China)

    2014-02-15

    Highlights: ► A Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} bulk metallic glass (BMG) with 50 GPa elastic modulus was used. ► This Ni-free Zr-based BMG had lower metal ion release rate than the commercial Ti. ► This Ni-free Zr-based BMG had better proteins adsorption than the commercial Ti. ► This Ni-free Zr-based BMG has a high potential for biomedical implant applications. -- Abstract: This study was conducted to investigate the surface characteristics, including the chemical composition, metal ion release, protein adsorption, and cell adhesion, of a Ni-free Zr-based (Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10}) bulk metallic glass (BMG) with low elastic modulus for biomedical implant applications. X-ray photoelectron spectroscopy was used to identify the surface chemical composition and the protein (albumin and fibronectin) adsorption of the specimen. The metal ions released from the specimen in simulated blood plasma and artificial saliva solutions were measured using an inductively coupled plasma-mass spectrometer. The cell adhesion, in terms of the morphology, focal adhesion complex, and skeletal arrangement, of human bone marrow mesenchymal stem cells was evaluated using scanning electron microscope observations and immunofluorescent staining. For comparison purposes, the above-mentioned tests were also carried out on the widely used biomedical metal, Ti. The results showed that the main component on the outermost surface of the amorphous Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} BMG was ZrO{sub 2} with small amounts of Cu, Al, and Fe oxides. The released metal ions from Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} BMG were well below the critical concentrations that cause negative biological effects. The Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} BMG had a greater adsorption capacity for albumin and fibronectin than that of commercial biomedical Ti. The Zr{sub 62.5}Cu{sub 22.5}Fe{sub 5}Al{sub 10} BMG surface showed an attached cell number similar

  13. Freeze-drying of proteins with glass-forming oligosaccharide-derived sugar alcohols.

    Science.gov (United States)

    Kadoya, Saori; Fujii, Kahori; Izutsu, Ken-ichi; Yonemochi, Etsuo; Terada, Katsuhide; Yomota, Chikako; Kawanishi, Toru

    2010-04-15

    Physical properties and protein-stabilizing effects of sugar alcohols in frozen aqueous solutions and freeze-dried solids were studied. Various frozen sugar alcohol solutions showed a glass transition of the maximally freeze-concentrated phase at temperatures (T(g)'s) that depended largely on the solute molecular weights. Some oligosaccharide-derived sugar alcohols (e.g., maltitol, lactitol, maltotriitol) formed glass-state amorphous cake-structure freeze-dried solids. Microscopic observation of frozen maltitol and lactitol solutions under vacuum (FDM) indicated onset of physical collapse at temperatures (T(c)) several degrees higher than their T(g)'s. Freeze-drying of pentitols (e.g., xylitol) and hexitols (e.g., sorbitol, mannitol) resulted in collapsed or crystallized solids. The glass-forming sugar alcohols prevented activity loss of a model protein (LDH: lactate dehydrogenase) during freeze-drying and subsequent storage at 50 degrees C. They also protected bovine serum albumin (BSA) from lyophilization-induced secondary structure perturbation. The glass-forming sugar alcohols showed lower susceptibility to Maillard reaction with co-lyophilized L-lysine compared to reducing and non-reducing disaccharides during storage at elevated temperature. Application of the oligosaccharide-derived sugar alcohols as alternative stabilizers in lyophilized protein formulations was discussed. Copyright 2010 Elsevier B.V. All rights reserved.

  14. Precision molding of advanced glass optics: innovative production technology for lens arrays and free form optics

    Science.gov (United States)

    Pongs, Guido; Bresseler, Bernd; Bergs, Thomas; Menke, Gert

    2012-10-01

    Today isothermal precision molding of imaging glass optics has become a widely applied and integrated production technology in the optical industry. Especially in consumer electronics (e.g. digital cameras, mobile phones, Blu-ray) a lot of optical systems contain rotationally symmetrical aspherical lenses produced by precision glass molding. But due to higher demands on complexity and miniaturization of optical elements the established process chain for precision glass molding is not sufficient enough. Wafer based molding processes for glass optics manufacturing become more and more interesting for mobile phone applications. Also cylindrical lens arrays can be used in high power laser systems. The usage of unsymmetrical free-form optics allows an increase of efficiency in optical laser systems. Aixtooling is working on different aspects in the fields of mold manufacturing technologies and molding processes for extremely high complex optical components. In terms of array molding technologies, Aixtooling has developed a manufacturing technology for the ultra-precision machining of carbide molds together with European partners. The development covers the machining of multi lens arrays as well as cylindrical lens arrays. The biggest challenge is the molding of complex free-form optics having no symmetrical axis. A comprehensive CAD/CAM data management along the entire process chain is essential to reach high accuracies on the molded lenses. Within a national funded project Aixtooling is working on a consistent data handling procedure in the process chain for precision molding of free-form optics.

  15. A thermodynamic approach towards glass-forming ability of amorphous metallic alloys

    Indian Academy of Sciences (India)

    Sonal R Prajapati; Supriya Kasyap; Arun Pratap

    2015-12-01

    A quantitative measure of the stability of a glass as compared to its corresponding crystalline state can be obtained by calculating the thermodynamic parameters, such as the Gibbs free energy difference (), entropy difference () and the enthalpy difference () between the super-cooled liquid and the corresponding crystalline phase. is known as the driving force of crystallization. The driving force of crystallization () provides very important information about the glass-forming ability (GFA) of metallic glasses (MGs). Lesser the driving force of crystallization more is the GFA. The varies linearly with the critical size (). According to Battezzati and Garonne the parameter ( = (1−(/))/(1−( / ))) in the expression for should be a constant (i.e., 0.8), but its uniqueness is not observed for all MGs. The thermal stability of various alloy compositions is studied by their undercooled liquid region ( = − ). Large implies greater stability against crystallization of the amorphous structure. Other GFA parameters are also calculated and correlated with critical size ().

  16. Theoretical study of miscibility and glass-forming trends in mixtures of polystyrene spheres

    Science.gov (United States)

    Shih, W.-H.; Stroud, D.

    1984-01-01

    A theoretical study of glass-forming trends and miscibility in mixtures of polystyrene spheres (polyballs) of different diameters, suspended in an aqueous solution, is presented. The polyballs are assumed to be charged and to interact via a Debye-Hueckel screened Coulomb potential. The Helmholtz free energy is calculated from a variational principle based on the Gibbs-Bogoliubov inequality, in which a mixture of hard spheres of different diameters is chosen as the reference system. It is found that when the charges of the two types of polyballs are sufficiently different, the variationally determined ratio of hard-sphere diameters differs substantially, leading to packing difficulties characteristic of glass formation. The experimentally observed range of glass formation corresponds to a ratio of hard-sphere diameters of 0.8 or less. Calculations of the free energy as a function of concentration indicate that the liquid polyball mixture is stable against the phase separation, even for widely different polyball charges.

  17. Surface engineering of a Zr-based bulk metallic glass with low energy Ar- or Ca-ion implantation.

    Science.gov (United States)

    Huang, Lu; Zhu, Chao; Muntele, Claudiu I; Zhang, Tao; Liaw, Peter K; He, Wei

    2015-02-01

    In the present study, low energy ion implantation was employed to engineer the surface of a Zr-based bulk metallic glass (BMG), aiming at improving the biocompatibility and imparting bioactivity to the surface. Ca- or Ar-ions were implanted at 10 or 50 keV at a fluence of 8 × 10(15)ions/cm(2) to (Zr0.55Al0.10Ni0.05Cu0.30)99Y1 (at.%) BMG. The effects of ion implantation on material properties and subsequent cellular responses were investigated. Both Ar- and Ca-ion implantations were suggested to induce atom displacements on the surfaces according to the Monte-Carlo simulation. The change of atomic environment of Zr in the surface regions as implied by the alteration in X-ray absorption measurements at Zr K-edge. X-ray photoelectron spectroscopy revealed that the ion implantation process has modified the surface chemical compositions and indicated the presence of Ca after Ca-ion implantation. The surface nanohardness has been enhanced by implantation of either ion species, with Ca-ion implantation showing more prominent effect. The BMG surfaces were altered to be more hydrophobic after ion implantation, which can be attributed to the reduced amount of hydroxyl groups on the implanted surfaces. Higher numbers of adherent cells were found on Ar- and Ca-ion implanted samples, while more pronounced cell adhesion was observed on Ca-ion implanted substrates. The low energy ion implantation resulted in concurrent modifications in atomic structure, nanohardness, surface chemistry, hydrophobicity, and cell behavior on the surface of the Zr-based BMG, which were proposed to be mutually correlated with each other. Published by Elsevier B.V.

  18. Dynamic behaviors of a Zr-based bulk metallic glass under ramp wave and shock wave loading

    Directory of Open Access Journals (Sweden)

    Binqiang Luo

    2015-06-01

    Full Text Available Dynamic behaviors of Zr51Ti5Ni10Cu25Al9 bulk metallic glass were investigated using electric gun and magnetically driven isentropic compression device which provide shock and ramp wave loading respectively. Double-wave structure was observed under shock compression while three-wave structure was observed under ramp compression in 0 ∼ 18GPa. The HEL of Zr51Ti5Ni10Cu25Al9 is 8.97 ± 0.61GPa and IEL is 8.8 ± 0.3GPa, respectively. Strength of Zr51Ti5Ni10Cu25Al9 estimated from HEL is 5.0 ± 0.3GPa while the strength estimated from IEL is 3.6 ± 0.1GPa. Shock wave velocity versus particle velocity curve of Zr51Ti5Ni10Cu25Al9 under shock compression appears to be bilinear and a kink appears at about 18GPa. The Lagrangian sound speed versus particle velocity curve of Zr51Ti5Ni10Cu25Al9 under ramp wave compression exhibits two discontinuances and are divided to three regions: elastic, plastic-I and plastic-II. The first jump-down occurs at elastic-plastic transition and the second appears at about 17GPa. In elastic and plastic-I regions, Lagrangian sound speed increases linearly with particle velocity, respectively. Characteristic response of sound speed in plastic-I region disagree with shock result in the same pressure region(7GPa ∼ 18GPa, but is consistent with shock result at higher pressure(18-110GPa.

  19. Achieving large macroscopic compressive plastic deformation and work-hardening-like behavior in a monolithic bulk metallic glass by tailoring stress distribution

    Science.gov (United States)

    Chen, L. Y.; Ge, Q.; Qu, S.; Jiang, Q. K.; Nie, X. P.; Jiang, J. Z.

    2008-05-01

    The limited plastic deformation and lack of work hardening seriously restrict the applications of bulk metallic glasses (BMGs). Here, large macroscopic compressive plastic deformation (over 15%) and work-hardening-like behavior were achieved in a monolithic BMG through tailoring loading stress distribution experimentally. Numerical analysis was also carried out to investigate the stress distribution under the same mechanical condition. It is shown that loading induced stress gradient is responsible for the achievement mentioned above.

  20. Ductile Damage and Fatigue Behavior of Semi-Finished Tailored Blanks for Sheet-Bulk Metal Forming Processes

    Science.gov (United States)

    Besserer, Hans-Bernward; Hildenbrand, Philipp; Gerstein, Gregory; Rodman, Dmytro; Nürnberger, Florian; Merklein, Marion; Maier, Hans Jürgen

    2016-03-01

    To produce parts from sheet metal with thickened functional elements, bulk forming operations can be employed. For this new process class, the term sheet-bulk metal forming has been established recently. Since sheet-bulk metal forming processes such as orbital forming generates triaxial stress and strain states, ductile damage is induced in the form of voids in the microstructure. Typical parts will experience cyclic loads during service, and thus, the influence of ductile damage on the fatigue life of parts manufactured by orbital forming is of interest. Both the formation and growth of voids were characterized following this forming process and then compared to the as-received condition of the ferritic deep drawing steel DC04 chosen for this study. Subsequent to the forming operation, the specimens were fatigued and the evolution of ductile damage and the rearrangement of the dislocation networks occurring during cyclic loading were determined. It was shown, that despite an increased ductile damage due to the forming process, the induced strain hardening has a positive effect on the fatigue life of the material. However, by analyzing the fatigued specimens a development of the ductile damage by an increasing number of voids and a change in the void shape were detected.

  1. Length scales in glass-forming liquids and related systems: a review

    Science.gov (United States)

    Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth

    2016-01-01

    The central problem in the study of glass-forming liquids and other glassy systems is the understanding of the complex structural relaxation and rapid growth of relaxation times seen on approaching the glass transition. A central conceptual question is whether one can identify one or more growing length scale(s) associated with this behavior. Given the diversity of molecular glass-formers and a vast body of experimental, computational and theoretical work addressing glassy behavior, a number of ideas and observations pertaining to growing length scales have been presented over the past few decades, but there is as yet no consensus view on this question. In this review, we will summarize the salient results and the state of our understanding of length scales associated with dynamical slow down. After a review of slow dynamics and the glass transition, pertinent theories of the glass transition will be summarized and a survey of ideas relating to length scales in glassy systems will be presented. A number of studies have focused on the emergence of preferred packing arrangements and discussed their role in glassy dynamics. More recently, a central object of attention has been the study of spatially correlated, heterogeneous dynamics and the associated length scale, studied in computer simulations and theoretical analysis such as inhomogeneous mode coupling theory. A number of static length scales have been proposed and studied recently, such as the mosaic length scale discussed in the random first-order transition theory and the related point-to-set correlation length. We will discuss these, elaborating on key results, along with a critical appraisal of the state of the art. Finally we will discuss length scales in driven soft matter, granular fluids and amorphous solids, and give a brief description of length scales in aging systems. Possible relations of these length scales with those in glass-forming liquids will be discussed.

  2. Glasses

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    2004-01-01

    The temperature dependence of the viscosity of most glassforming liquids is known to depart significantly from the classical Arrhenius behaviour of simple fluids. The discovery of an unexpected correlation between the extent of this departure and the Poisson ratio of the resulting glass could lead...... to new understanding of glass ageing and viscous liquid dynamics....

  3. Glasses

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    2004-01-01

    The temperature dependence of the viscosity of most glassforming liquids is known to depart significantly from the classical Arrhenius behaviour of simple fluids. The discovery of an unexpected correlation between the extent of this departure and the Poisson ratio of the resulting glass could lead...... to new understanding of glass ageing and viscous liquid dynamics....

  4. Evolution of shear bands, free volume, and structure in room temperature rolled Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yuanli; Shi, Bo; Ma, Zhikun; Li, Jiangong, E-mail: lijg@lzu.edu.cn

    2015-01-19

    The evolution of the shear band, free volume, and structure in room temperature rolled Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass was investigated. It was found that the average shear band density increases monotonously with increasing strain. For the room temperature rolled Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass with a strain of 99%, a high density of shear bands with an average spacing of 31 nm was observed. The absolute free volume content was determined based on the free volume model and found to increase monotonously with increasing strain. The free volume content in the room temperature rolled Pd{sub 40}Ni{sub 40}P{sub 20} bulk metallic glass with a strain of 99% is 34% higher than its as-cast counterpart. Neither phase separation nor crystallization occurs in all the deformed samples. The coordination number of the first coordination shell decreases and the degree of disorder of atomic arrangement increases with increasing strain.

  5. Workability of the supercooled liquid in the Zr{sub 65}Al{sub 10}Ni{sub 10}Cu{sub 15} bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, Y.; Shibata, T.; Inoue, A.; Masumoto, T. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

    1997-12-19

    The workability of the supercooled liquid in metallic glass has been examined through the extrusion of a Zr{sub 6.5}Al{sub 10}Ni{sub 10}Cu{sub 15} at.% bulk glassy alloy with a wide supercooled liquid region. The metallic glass exhibited superplastic-like deformation behavior at high strain rates, resulting in an excellent workability. The working throughout a wide range of extrusion conditions was compatible with retaining the glass phase and the original strength. The extrusion maps and the expression between extrusion temperature, pressure and ram-speed have been established. Moreover, the features of working such as the Barus effect and the advantage of a small stepwise increase in strain rate have been revealed.

  6. Coercivity of the Nd–Fe–B hot-deformed magnets diffusion-processed with low melting temperature glass forming alloys

    Energy Technology Data Exchange (ETDEWEB)

    Seelam, U.M.R. [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Liu, Lihua [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan); Akiya, T.; Sepehri-Amin, H.; Ohkubo, T. [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Sakuma, N.; Yano, M.; Kato, A. [Advanced Material Engineering Division, Toyota Motor Corporation, Susono 410-1193 (Japan); Hono, K., E-mail: kazuhiro.hono@nims.go.jp [Elements Strategy Initiative Center for Magnetic Materials (ESICMM), National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-8571 (Japan)

    2016-08-15

    Nd- and Pr-based alloys with bulk glass forming ability and low melting temperatures, Nd{sub 60}Al{sub 10}Ni{sub 10}Cu{sub 20} and Pr{sub 60}Al{sub 10}Ni{sub 10}Cu{sub 20}, were used for grain boundary diffusion process to enhance the coercivity of hot-deformed magnets. The coercivity increment was proportional to the weight gain after the diffusion process. For the sample with 64% weight gain, the coercivity increased up to 2.8 T, which is the highest value for bulk Nd–Fe–B magnets that do not contain heavy rare-earth elements, Dy or Tb. Approximately half of the intergranular regions were amorphous and the remaining regions were crystalline. Magnetic isolation of the Nd{sub 2}Fe{sub 14}B grains by the Nd-rich amorphous/crystalline intergranular phases is attributed to the large coercivity enhancement. The coercivity does not change after the crystallization of the intergranular phase, indicating that the coercivity is not influenced by the strain at the interface with the crystalline intergranular phase. - Highlights: • Bulk-glass forming alloys were infiltrated into hot-deformed Nd–Fe–B magnets. • Very high coercivity of 2.8 T was attained without heavy rare-earth elements. • Approximately half of the inter-granular regions were amorphous. • Crystallization of amorphous intergranular phase does not change coercivity.

  7. Anomalous diffusion in heterogeneous glass-forming liquids: temperature-dependent behavior.

    Science.gov (United States)

    Langer, J S

    2008-11-01

    In a preceding paper, Langer and Mukhopadhyay [Phys. Rev. E 77, 061505 (2008)] studied the diffusive motion of a tagged molecule in an heterogeneous glass-forming liquid at temperatures just above a glass transition. Among other features of this system, we postulated a relation between heterogeneity and stretched-exponential decay of correlations, and we also confirmed that systems of this kind generally exhibit non-Gaussian diffusion on intermediate length and time scales. Here I extend this analysis to higher temperatures approaching the point where the heterogeneities disappear and thermal activation barriers become small. I start by modifying the continuous-time random-walk theory proposed in Langer and Mukhopadhyay and supplement this analysis with an extension of the excitation-chain theory of glass dynamics. I also use a key result from the shear-transformation-zone theory of viscous deformation of amorphous materials. Elements of each of these theories are then used to interpret experimental data for orthoterphenyl, specifially, the diffusion and viscosity coefficients and neutron-scattering measurements of the self-intermediate scattering function. Reconciling the theory with these data sets provides insights into the crossover between super-Arrhenius and Arrhenius dynamics, length scales of spatial heterogeneities, violation of the Stokes-Einstein relation in glass-forming liquids, and the origin of stretched-exponential decay of correlations.

  8. Al基块体金属玻璃的研究进展%Research Progress in Al-based Bulk Metallic Glasses

    Institute of Scientific and Technical Information of China (English)

    陈思泉; 李艳辉; 张伟

    2016-01-01

    Al-based metallic glasses (MGs)exhibit high strength,high toughness,and good corrosion resis-tance.Especially,Al-based MGs possess high special strength which is up to 330 kN·m/kg.Therefore,Al-based MGs are promising for applications as a new type of structural materials in aerospace fields.In recent years,Al-based MGs with high glass-forming ability (GFA)and high supercooled liquid stability have been developed,and the MG samples in bulk form have been produced via copper mold casting and consolidation of Al-based MG powders as well, which will promote their practical use.In this paper,the research progress in the development,GFA,stabilization of supercooled liquid,and mechanical properties of Al-based MGs,together with the structure and properties of sintered Al-based MGs powder are reviewed.The problems during the development of the alloys are discussed.%Al基金属玻璃具有高强度、高韧性、良好的耐蚀性,特别是其比强度高达330 kN·m/kg,作为新结构材料在航空航天领域具有潜在的应用前景。近年不仅研发出了具有大过冷液相区以及能形成块体金属玻璃的Al基合金,还通过粉体温热固化成形工艺实现了Al基金属玻璃的大块体化,推动了其在实际生产中的应用。简述了有关Al基金属玻璃合金的玻璃形成能力、过冷液体热稳定性、力学性能及其粉末烧结体的组织和性能等方面的最新研究进展,并对其发展存在的问题进行了探讨。

  9. Anomalous Crystallization as a Signature of the Fragile-to-Strong Transition in Metallic Glass-Forming Liquids

    DEFF Research Database (Denmark)

    Yang, X.N.; Zhou, C.; Sun, Q.J.;

    2014-01-01

    We study the fragile-to-strong (F−S) transition of metallic glass-forming liquids (MGFLs) by measuring the thermal response during annealing and dynamic heating of La55Al25Ni5Cu15 glass ribbons fabricated at different cooling rates. We find that the glasses fabricated in the intermediate regime...... of cooling rates (15−25 m/s) exhibit an anomalous crystallization behavior upon reheating as compared to the glasses formed at other cooling rates. This anomalous crystallization behavior implies the existence of a thermodynamic F−S transition, could be used as an alternative method for detecting the F...

  10. Predicting Composition Dependence of Glass Forming Ability in Ternary Al-Cu-Y System by Thermodynamic Calculation

    Directory of Open Access Journals (Sweden)

    Qi Wang

    2014-11-01

    Full Text Available The composition dependence of glass forming ability in the ternary Al-Cu-Y system is predicted by thermodynamic calculations based on the Miedema’s model and Alonso’s method. By comparing the relative energetic status of the amorphous phase versus the solid solution phase, a hexagonal composition region that energetically favoring the metallic glass formation is predicted. The glass formation driving force and crystallization resistance are further calculated and the composition of Al72Cu10Y18 is pinpointed with the largest glass forming ability in the Al-Cu-Y system. The calculation results are well supported by the experimental observations reported in the literature.

  11. Direct Observation on the Evolution of Shear Banding and Buckling in Tungsten Fiber Reinforced Zr-Based Bulk Metallic Glass Composite

    Science.gov (United States)

    Chen, J. H.; Chen, Y.; Jiang, M. Q.; Chen, X. W.; Fu, H. M.; Zhang, H. F.; Dai, L. H.

    2014-11-01

    The evolution of micro-damage and deformation of each phase in the composite plays a pivotal role in the clarification of deformation mechanism of composite. However, limited model and mechanical experiments were conducted to reveal the evolution of the deformation of the two phases in the tungsten fiber reinforced Zr-based bulk metallic glass composite. In this study, quasi-static compressive tests were performed on this composite. For the first time, the evolution of micro-damage and deformation of the two phases in this composite, i.e., shear banding of the metallic glass matrix and buckling deformation of the tungsten fiber, were investigated systematically by controlling the loading process at different degrees of deformation. It is found that under uniaxial compression, buckling of the tungsten fiber occurs first, while the metallic glass matrix deforms homogeneously. Upon further loading, shear bands initiate from the fiber/matrix interface and propagate in the metallic glass matrix. Finally, the composite fractures in a mixed mode, with splitting in the tungsten fiber, along with shear fracture in the metallic glass matrix. Through the analysis on the stress state in the composite and resistance to shear banding of the two phases during compressive deformation, the possible deformation mechanism of the composite is unveiled. The deformation map of the composite, which covers from elastic deformation to final fracture, is obtained as well.

  12. Changes in dynamics of the glass-forming pharmaceutical nifedipine in binary mixtures with octaacetylmaltose.

    Science.gov (United States)

    Kaminska, E; Tarnacka, M; Kaminski, K; Ngai, K L; Paluch, M

    2015-11-01

    Some molecular glass-formers can crystallize in the glassy state, some of which are van der Waals molecules and some are pharmaceuticals. The molecular mechanism responsible for this glass-to-crystal mode of crystallization is of interest to the glass transition research community as well as to the pharmaceutical industry because the effect is detrimental to stability of amorphous form of the drugs stored below the glass transition temperature. Two prominent models have been proposed for the molecular mechanism. In the homogeneous nucleation-based crystallization model, the molecular mechanism is the secondary relaxation, and the other model assumes that the molecular process responsible for crystal growth in the glassy state is from the local molecular motions. Crystal growth requires motion of the entire molecule, and in the glassy state the only such local molecular motion is engendered by the secondary relaxation of the Johari-Goldstein (JG) kind. While the JG secondary relaxation is the crux in the two models of glass-to-crystal growth, it has not been found in the glassy state of the pharmaceuticals studied so far. The examples include 5-methyl-2-[(2-nitrophenyl)amino]-3-thiophenecarbonitrile (ROY), indomethacin (IMC) and nifedipine (NIF). In the absence of any evidence of the JG secondary relaxation, the conundrum is that the two models of glass-to-crystal growth cannot be validated. It turns out these pharmaceuticals all have structural α-relaxations with narrow frequency dispersion. Empirically, glass-formers with narrow α-dispersion have JG secondary relaxation with weak relaxation strength, not well separated from the α-relaxation, and hence cannot be resolved. Theoretically, the narrow width of the α-dispersion is due to weak intermolecular coupling. In this article we enhance the intermolecular coupling of NIF by mixing with octaacetylmaltose to enhance the intermolecular coupling of NIF. In this way we have successfully resolved the JG secondary

  13. Ageing, rheology and effective temperature in a glass-forming system

    CERN Document Server

    Barrat, J L

    2003-01-01

    In this paper, I review some of the recent results obtained, using molecular dynamics simulations, on the out-of-equilibrium behaviour of glass-forming systems. Both the ageing (evolution after a fast quench in the glassy phase) and the driven (evolution under uniform shear flow) situations are considered. The theoretical concept of effective temperature that was shown to characterize such nonequilibrium states well is also discussed.

  14. Source of non-arrhenius average relaxation time in glass-forming liquids

    DEFF Research Database (Denmark)

    Dyre, Jeppe

    1998-01-01

    A major mystery of glass-forming liquids is the non-Arrhenius temperature-dependence of the average relaxation time. This paper briefly reviews the classical phenomenological models for non-Arrhenius behavior – the free volume model and the entropy model – and critiques against these models. We...... are anharmonic, the non-Arrhenius temperature-dependence of the average relaxation time is a consequence of the fact that the instantaneous shear modulus increases upon cooling....

  15. Development of thermally formed glass optics for astronomical hard X-ray telescopes

    DEFF Research Database (Denmark)

    Craig, W.W.; Hailey, C.J.; Jimenez-Garate, M.

    2000-01-01

    The next major observational advance in hard X-ray/soft gamma-ray astrophysics will come with the implementation of telescopes capable of focusing 10-200 keV radiation. Focusing allows high signal-to-noise imaging and spectroscopic observations of many sources in this band for the first time. The...... report on new, thermally-formed glass micro-sheet optics capable of meeting the requirements of the next-generation of astronomical hard X-ray telescopes....

  16. Crack initiation and fracture features of Fe–Co–B–Si–Nb bulk metallic glass during compression

    Directory of Open Access Journals (Sweden)

    S. Lesz

    2016-01-01

    Full Text Available The aim of the paper was investigation crack initiation and fracture features developed during compression of Fe-based bulk metallic glass (BMG. These Fe-based BMG has received great attention as a new class of structural material due to an excellent properties (e.g. high strength and high elasticity and low costs. However, the poor ductility and brittle fracture exhibited in BMGs limit their structural application. At room temperature, BMGs fails catastrophically without appreciable plastic deformation under tension and only very limited plastic deformation is observed under compression or bending. Hence a well understanding of the crack initiation and fracture morphology of Fe-based BMGs after compression is of much importance for designing high performance BMGs. The raw materials used in this experiment for the production of BMGs were pure Fe, Co, Nb metals and nonmetallic elements: Si, B. The Fe–Co–B–Si–Nb alloy was cast as rods with three different diameters. The structure of the investigated BMGs rod is amorphous. The measurement of mechanical properties (Young modulus - E, compressive stress - σc, elastic strain - ε, unitary elastic strain energy – Uu were made in compression test. Compression test indicates the rods of Fe-based alloy to exhibit high mechanical strength. The development of crack initiation and fracture morphology after compression of Fe-based BMG were examined with scanning electron microscope (SEM. Fracture morphology of rods has been different on the cross section. Two characteristic features of the compressive fracture morphologies of BMGs were observed. One is the smooth region. Another typical feature of the compressive fracture morphology of BMGs is the vein pattern. The veins on the compressive fracture surface have an obvious direction as result of initial displace of sample along shear bands. This direction follows the direction of the displacement of a material. The formation of veins on the

  17. Thermodynamic and relative approach to compute glass-forming ability of oxides

    Indian Academy of Sciences (India)

    Nouar Boubata; Abdelmalek Roula; Islam Moussaoui

    2013-06-01

    This study deals with the evaluation of glass-forming ability (GFA) of oxides and is a critical reading of Sun and Rawson thermodynamic approach to quantify this aptitude. Both approaches are adequate but ambiguous regarding the behaviour of some oxides (tendency to amorphization or crystallization). Indeed, ZrO2 and Al2O3 were inappropriately listed by Sun and Rawson to be glassformer oxides while being intermediate ones.We present a non-dimensional approach to value GFA of single oxide by affecting to each one of the coefficients (without measuring units). Obeying to the non-dimensional analysis rules, we introduce a neglected (in all prior thermodynamic models) characteristic: the isobaric heat capacity (p) of oxides, and execute a mathematical treatment of oxides thermodynamic data.We note this coefficient as thermodynamical relative glass-forming ability (ThRGFA) and formulate a model to compute it. Computed values of 2nd, 3rd, 4th and 5th period metal oxides reveal a clear differentiation between them. Indeed, all glass former oxides are characterized by ThRGFA values over 1.709. Moreover, the value intervals confirm the oxides classification into three groups (forming, intermediate and modifier) and sorting of the former ones in distinctive strong and fragile oxides.

  18. Mineralogy and thermodynamic properties of magnesium phyllosilicates formed during the alteration of a simplified nuclear glass

    Science.gov (United States)

    Debure, Mathieu; De Windt, Laurent; Frugier, Pierre; Gin, Stéphane; Vieillard, Philippe

    2016-07-01

    The precipitation of crystallized magnesium phyllosilicates generally sustains the alteration rate of nuclear waste containment glass. However, glass alteration slows down to a residual rate as soon as Mg disappears from the solution. The identification of the phyllosilicates formed is therefore crucial for modeling the long-term behavior of nuclear glass. This study deals with batch alteration of the simplified nuclear glass ISG in presence of magnesium, and the characterization of the secondary phases. Morphological, chemical and structural analyses (MET, EDX, XRD) were performed to determine the nature and structure of the precipitated phases identified as trioctahedral smectites. Analyses conducted on the secondary phases proved the presence of Al, Na and Ca in the Mg-phyllosilicate phases. Such elements had been suspected but never quantitatively measured. The experimental results were then used to determine the thermodynamic solubility constants for each precipitated secondary phase at various temperatures. The calculated values were consistent with those available for sodium and magnesium saponites in the existing thermodynamic databases.

  19. Dynamic mechanical behavior and high pressure phase stability of a zirconium-based bulk metallic glass and its composite with tungsten

    Science.gov (United States)

    Martin, Morgana

    2008-10-01

    failure stress over the range of strain rates evaluated, and work-hardening decreased as strain-rate increased. Its deformation mode was found to transition from heterogeneous deformation below the glass transition temperature (of the BMG), to homogeneous deformation between the glass transition and crystallization temperatures, and then back to heterogeneous deformation behavior above the crystallization temperature. The composite exhibited a large susceptibility to shear failure, as evidenced by much decreased strain-to-failure in biaxial (compression-shear) specimens as compared to that in uniaxial (compression) specimens. Failure took place primarily in the glass matrix and at the tungsten particle interfaces at all strain rates. Overall, the deformation and failure behavior of the composite is dominated by that of tungsten, but characteristics of BMG deformation and failure are evident, especially between the glass transition and crystallization temperatures, and at extremely high strain rates. For the monolithic BMG, fracture surfaces became increasingly more disorganized as strain rate increased, with evidence of melting due to temperature rise during fracture. The deformation and elastic-plastic wave propagation and interaction response based on measured free surface velocity traces of the monolithic glass were quite well described by the pressure-hardening Drucker-Prager model. Likewise, the deformation response of the composite was described reasonably well considering a rule of mixtures combination of properties of the BMG and W. High-pressure equation of state experiments provided evidence of transition to a mixed phase region (at ˜26 GPa) and then to a high-pressure phase (at ˜67 GPa) with a bulk modulus of 288 GPa, 144% higher than that of the bulk modulus of the ambient pressure. Specimens obtained from recovery experiments did not reveal any crystallization, indicating that any crystallites that may have formed were too small and too few to detect

  20. Determination of Lubricant Bulk Modulus in Metal Forming by Means of a Simple Laboratory Test and Inverse FEM Analysis

    DEFF Research Database (Denmark)

    Hafis, S. M.; Christiansen, P.; Martins, P. A. F.

    2016-01-01

    The influence of workpiece surface topography on friction, lubrication and final surface equality in metal forming operations is well known and has been pointed out by many researchers.This is especially the case when liquid lubricants are applied in situations, where increased surface roughness...... a simple, practical test to determine the bulk modulus. Combination of the experimental upsetting of an axisymmetric metal workpiece containing a truncated conical surface pocket with an inverse finite element analysis of the test allows determining the lubricant bulk modulus. The finite element analysis...... couples lubricant flow with plastic deformation of the metal directly. Results show that the proposed procedure allows determining an approximate bulk modulus for the lubricant....

  1. The e/a factor governing the formation and stability of (Zr{sub 76}Ni{sub 24}){sub 1-x}Al{sub x} bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y.M.; Shek, C.H.; Qiang, J.B.; Wong, C.H.; Chen, W.R.; Dong, C

    2003-06-15

    In the present paper (Zr{sub 76}Ni{sub 24}){sub 1-x}Al{sub x} alloys were prepared to investigate the influence of e/a, electron number per atom, on their glass-forming abilities. The bulk metallic glasses (BMGs) obtained in this alloy series have an e/a span from 1.37 to 1.53. Their thermal stability increases with the e/a ratios. The largest thermal stability is found at Zr{sub 60}Al{sub 21}Ni{sub 19} with the highest possible e/a=1.53. These BMGs manifest negative temperature coefficients of resistivity and a nearly linear T-dependence of resistivity within the temperature span 80-293 K. The validity of the Nagel-Tauc conjecture, 2k{sub f}{approx}k{sub p} for the stabilities of these BMGs is discussed. The e/a-based rule is a promising way to locate glass-forming compositions in the Zr-based multi-component alloy systems.

  2. Room temperature gas-solid reaction of titanium on glass surfaces forming a very low resistivity layer

    OpenAIRE

    Hugo Solís; Neville Clark; Daniel Azofeifa; E. Avendano

    2016-01-01

    Titanium films were deposited on quartz, glass, polyamide and PET substrates in a high vacuum system at room temperature and their electrical resistance monitored in vacuo as a function of thickness. These measurements indicate that a low electrical resistance layer is formed in a gas-solid reaction during the condensation of the initial layers of Ti on glass and quartz substrates. Layers begin to show relative low electrical resistance at around 21 nm for glass and 9nm for quartz. Samples de...

  3. Observation and computer simulation of multicomponent chemical short-range order (MCSRO) for the bulk metallic glasses

    Institute of Scientific and Technical Information of China (English)

    Guoliang Chen; Xidong Hui; Kefu Yao; Huaiyu Hou; Xiongjun Liu; Meiling Wang; Guang Chen

    2005-01-01

    The atomic configuration of chemical short-range order (CSRO) for the Zr-base metallic glasses was investigated by using nano-diffraction and high resolution transmission electronic microscopy (HRTEM) technology with a beam size of 0.5 nm. It is illustrated that the pattern of atomic configuration of CSRO might have various compound counterparts because of the chemical interaction of bonding atoms. Some atomic configuration of MCSRO is similar to the icosahedral structure with 10-fold symmetry of very weak spots. In deed, the nano-beam technology could clearly detect the evolution of atomic configuration in nanometer scale during the transformation from the metallic melt to the primary crystallization. The local atomic configuration of CSRO is also investigated by molecular dynamics simulation (MD) for the Zr2Ni compound in a wider temperature range. The CSRO in the melt could be pictorially demonstrated as distorted coordination polyhedron of the compound structure and/or the structure similar to cubo-octahedron analogs. The MD simulation illustrates that the atomic packing of long-range order disappears just above the melting point, but the chemical interaction of bonding atoms still exists that leads to form the various CSRO with the atomic configuration similar to stable or metastable unit cell of Zr2Ni compound. The icosahedral polyhedron became more abundance as the overheating temperature was raised.

  4. Serration Behavior in Zr-Cu-Al Glass-forming Systems

    Institute of Scientific and Technical Information of China (English)

    Zhong WANG; Jiao-jiao LI; Li-wei REN; Yong ZHANG; Jun-wei QIAO; Bao-cheng WANG

    2016-01-01

    The metallic glass matrix composites (MGMCs)and bulk metallic glasses (BMGs)were studied by statis-tical analysis during plastic deformation at the strain rates of 2×10 -2 ,2×10 -3 ,and 2×10 -4 s-1 ,respectively.No serration events occur in both MGMCs and BMGs during compression tests at the strain rate of 2×10 -2 s-1 .When deformed at the strain rate of 2×10 -3 s-1 ,the BMG displays a larger plasticity,which is due to the larger serration events followed by a series of small serrations caused by the continuous movement of free volume.The amplitudes and elastic-energy densities increase with increasing the strain rates owing to many serrations in MGMCs.It is deduced that the Young′s modulus decreases from the normalized stress drop and fluctuations are observed on stress-strain curves,which is attributed to a lower coefficient according to the stick-slip model.

  5. Metallic Glass Formation by Ion Mixing and Calculation of Glass-Forming-Ability from Inter-Atomic Potential in the Binary Metal Systems

    Institute of Scientific and Technical Information of China (English)

    LI Zhengcao; LAI Wensheng; LIU Baixin

    2001-01-01

    In this article,a brief summary of the up-to-date progress of metallic glass formation by ion mixing of metallic multilayers in the binary metal systems is first presented.Secondly,thermodynamic modeling of metallic glass formation is developed with special consideration of the interfacial free energy of the multilayers.Thirdly,results of molecular dynamics simulations for some representative systems are presented to show the calculation of the glass-forming ability directly from the inter-atomic potential of the binary metal systems.

  6. Nonvibrating granular model for a glass-forming liquid: Equilibration and aging

    Science.gov (United States)

    Tapia-Ignacio, C.; Garcia-Serrano, J.; Donado, F.

    2016-12-01

    We studied experimentally a model of a glass-forming liquid on the basis of a nonvibrating magnetic granular system under an unsteady magnetic field. A sudden quenching was produced that drove the system from a liquid state to a different final state with lower temperature; the latter could be a liquid state or a solid state. We determined the mean-squared displacement in temporal windows to obtain the dynamic evolution of the system, and we determined the radial distribution function to obtain its structural characteristics. The results were analyzed using the intermediate scattering function and the effective potential between two particles. We observed that when quenching drives the system to a final state in the liquid phase far from the glass-transition temperature, equilibration occurs very quickly. When the final state has a temperature far below the glass-transition temperature, the system reaches its equilibrium state very quickly. In contrast, when the final state has an intermediate temperature but is below that corresponding to the glass transition, the system falls into a state that evolves slowly, presenting aging. The system evolves by an aging process toward more ordered states. However, after a waiting time, the dynamic behavior changes. It was observed that some particles get close enough to overpass the repulsive interactions and form small stable aggregates. In the effective potential curves, it was observed that the emergence of a second effective well due to the attraction quickly evolves and results in a deeper well than the initial effective well due to the repulsion. With the increase in time, more particles fall in the attractive well forming inhomogeneities, which produce a frustration in the aging process.

  7. Strong work-hardening behavior induced by the solid solution strengthening of dendrites in TiZr-based bulk metallic glass matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Ma, D.Q. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Jiao, W.T. [College of Education, Hebei Normal University of Science and Technology, Qinhuangdao 066004 (China); Zhang, Y.F. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Hebei Vocational and Technical College of Building Materials, Qinhuangdao 066004 (China); Wang, B.A.; Li, J.; Zhang, X.Y. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Ma, M.Z., E-mail: mz550509@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Liu, R.P. [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

    2015-03-05

    Highlights: • Hardness of dendrite of TiZr-based BMGMCs increases. • Strong work-hardening behavior is obtained after solid solution strengthening. • Lattice distortions of dendrite suffering from rapid cooling are detected. - Abstract: A series of TiZr-based bulk metallic glass matrix composites (BMGMCs) with distinguished mechanical properties are successfully fabricated by adding different volume fractions of Ta (Ti{sub 38.8}Zr{sub 28.8}Cu{sub 6.2}Be{sub 16.2}Nb{sub 10} as the basic composition, denoted as Ta{sub 0.0}–Ta{sub 8.0}). Along with the growth of precipitated phase, typical dendritic morphology is fully developed in the TiZr-based BMGMCs of Ta{sub 8.0}. Energy-dispersive spectrometry analysis of the dendrites and glass matrix indicates that the metallic elements of Nb and Ta should preferentially form solid solution into dendrites. The chaotic structure of high-temperature precipitate phase is trapped down by the rapid cooling of the copper-mould. The detected lattice distortions in the dendrites are attributed to the strong solid solution strengthening of the metallic elements of Ti, Zr, Nb, and Ta. These lattice distortions increase the resistance of the dislocation motion and pin the dislocations, thus the strength and hardness of dendrite increase. Dendrites create a strong barrier for the shear band propagation and generate multiple shear bands after solid solution strengthening, thereby providing the TiZr-based BMGMCs with greatly improved capacity to sustain plastic deformation and resistance to brittle fracture. Thus, the TiZr-based BMGMCs possess distinguished work-hardening capability. Among these TiZr-based BMGMCs, the sample Ta{sub 0.5} possesses the largest plastic strain (ε{sub p}) at 20.3% and ultimate strength (σ{sub max}) of 2613 MPa during compressive loading. In addition, the sample of Ta{sub 0.5} exhibits work-hardening up to an ultrahigh tensile strength of 1680 MPa during the tensile process, and then progressively

  8. Manipulating femtosecond laser interactions in bulk glass and thin-film with spatial light modulation (Conference Presentation)

    Science.gov (United States)

    Alimohammadian, Ehsan; Ho, Stephen; Ertorer, Erden; Gherghe, Sebastian; Li, Jianzhao; Herman, Peter R.

    2017-03-01

    Spatial Light Modulators (SLM) are emerging as a power tool for laser beam shaping whereby digitally addressed phase shifts can impose computer-generated hologram patterns on incoming laser light. SLM provide several additional advantages with ultrashort-pulsed lasers in controlling the shape of both surface and internal interactions with materials. Inside transparent materials, nonlinear optical effects can confine strong absorption only to the focal volume, extend dissipation over long filament tracks, or reach below diffraction-limited spot sizes. Hence, SLM beam shaping has been widely adopted for laser material processing applications that include parallel structuring, filamentation, fiber Bragg grating formation and optical aberration correction. This paper reports on a range of SLM applications we have studied in femtosecond processing of transparent glasses and thin films. Laser phase-fronts were tailored by the SLM to compensate for spherical surface aberration, and to further address the nonlinear interactions that interplay between Kerr-lens self-focusing and plasma defocusing effects over shallow and deep focusing inside the glass. Limits of strong and weak focusing were examined around the respective formation of low-loss optical waveguides and long uniform filament tracks. Further, we have employed the SLM for beam patterning inside thin film, exploring the limits of phase noise, resolution and fringe contrast during interferometric intra-film structuring. Femtosecond laser pulses of 200 fs pulse duration and 515 nm wavelength were shaped by a phase-only LCOS-SLM (Hamamatsu X10468-04). By imposing radial phase profiles, axicon, grating and beam splitting gratings, volume shape control of filament diameter, length, and uniformity as well as simultaneous formation of multiple filaments has been demonstrated. Similarly, competing effects of spherical surface aberration, self-focusing, and plasma de-focusing were studied and delineated to enable formation

  9. Improvement of the thermoplastic formability of Zr65Cu17.5Ni10Al7.5 bulk metallic glass by minor addition of Erbium

    Science.gov (United States)

    Hu, Q.; Zeng, X. R.; Fu, M. W.; Chen, S. S.; Jiang, J.

    2016-12-01

    The softness of Zr65Cu17.5Ni10Al7.5 bulk metallic glass (BMG) in the super-cooled liquid range (SCLR) is obviously improved by minor addition of 2% Er, which makes (Zr65Cu17.5Ni10Al7.5)98Er2 (Zr65Er2) to be a very formable Be-free Zr-based BMG. It is found the lower glass transition temperature of Zr65Er2 has an important contribution to the improvement of formability, which is contrary to the general understanding that the larger fragility and wider super-cooled liquid region (SCLR) are the major reasons for better thermoplastic formability. This finding is well explained by using the linear simplification of the SCLR in Angell plot. Zr65Er2 also has lower crystallization temperature and melting temperature, which is believed to be related to the formation of short-range ordering with lower transition energy rather than the composition shift to near eutectic. The above results help understand the effect of minor addition of rare-earth to the formability of Zr-based bulk metallic glasses.

  10. Amorphization within the tablet: Using microwave irradiation to form a glass solution in situ.

    Science.gov (United States)

    Doreth, Maria; Hussein, Murtadha Abdul; Priemel, Petra A; Grohganz, Holger; Holm, René; Lopez de Diego, Heidi; Rades, Thomas; Löbmann, Korbinian

    2017-03-15

    In situ amorphization is a concept that allows to amorphize a given drug in its final dosage form right before administration. Hence, this approach can potentially be used to circumvent recrystallization issues that other amorphous formulation approaches are facing during storage. In this study, the feasibility of microwave irradiation to prepare amorphous solid dispersions (glass solutions) in situ was investigated. Indomethacin (IND) and polyvinylpyrrolidone K12 (PVP) were tableted at a 1:2 (w/w) ratio. In order to study the influence of moisture content and energy input on the degree of amorphization, tablet formulations were stored at different relative humidity (32, 43 and 54% RH) and subsequently microwaved using nine different power-time combinations up to a maximum energy input of 90kJ. XRPD results showed that up to 80% (w/w) of IND could be amorphized within the tablet. mDSC measurements revealed that with increasing microwaving power and time, the fractions of crystalline IND and amorphous PVP reduced, whereas the amount of in situ formed IND-PVP glass solution increased. Intrinsic dissolution showed that the dissolution rate of the microwaved solid dispersion was similar to that of a quench cooled, fully amorphous glass solution even though the microwaved samples contained residual crystalline IND. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. Fluctuations and Shape of Cooperative Rearranging Regions in Glass-Forming Liquids

    Science.gov (United States)

    Biroli, Giulio; Cammarota, Chiara

    2017-01-01

    We develop a theory of amorphous interfaces in glass-forming liquids. We show that the statistical properties of these surfaces, which separate regions characterized by different amorphous arrangements of particles, coincide with the ones of domain walls in the random field Ising model. A major consequence of our results is that supercooled liquids are characterized by two different static lengths: the point-to-set ξPS , which is a measure of the spatial extent of cooperative rearranging regions, and the wandering length ξ⊥, which is related to the fluctuations of their shape. We find that ξ⊥ grows when approaching the glass transition but slower than ξPS. The wandering length increases as sc-1 /2, where sc is the configurational entropy. Our results strengthen the relationship with the random field Ising model found in recent works. They are in agreement with previous numerical studies of amorphous interfaces and provide a theoretical framework for explaining numerical and experimental findings on pinned particle systems and static lengths in glass-forming liquids.

  12. Microcraters formed in hot glass by hypervelocity projectiles. [lunar environment simulation

    Science.gov (United States)

    Vedder, J. F.

    1976-01-01

    Microcraters were formed in heated soda-lime glass by the normal incidence of spheres of plastic or fused silica with diameters between 0.8 and 4.5 microns and velocities between 2.5 and 10 km/s. The morphology of the craters in targets at temperatures up to 800 C is little different from those formed in unheated glass. Spallation still occurs to the same extent and above the same velocity threshold, but the spalls sag and sharp edges become dull in a few seconds at temperatures above the softening point. There is a small increase in the flow of glass from the central pit into a narrow lip at the higher temperatures, but this lip is often removed by spallation, especially at the higher velocities of impact. There is no evidence of a splashed lip with strings of melt overlying the spalled area. The results in conjunction with other evidence suggest that most lunar craters of micrometer size with a smooth central pit, splashed lip, and a spallation zone are the result of primary impacts.

  13. Temperature dependence of the Landau-Placzek ratio in glass forming liquids.

    Science.gov (United States)

    Popova, V A; Surovtsev, N V

    2011-10-07

    Here, we studied Rayleigh-Brillouin light scattering in ten different glass-forming liquids (α-picoline, toluene, o-toluidine, ethanol, salol, glycerol, dibutyl phthalate, o-terphenyl, propylene carbonate, and propylene glycol). For each of these liquids it was found that the Landau-Placzek ratio is in a good agreement with the theory at high temperatures and significantly exceeds the theoretical prediction below a certain temperature. Transition between the two temperature regimes occurs near T(A), where T(A) is crossover point from an Arrhenius-like to a non-Arrhenius behavior for the α-relaxation time dependence on temperature. Increase of the Landau-Placzek ratio relative to the theoretical prediction below T(A) seems to be the universal feature of glass-formers. We suggest that formation of locally favored structures in liquids below T(A) causes observed excess of the Landau-Placzek ratio.

  14. Thermal and relaxational properties of glass-forming material, 3,3-dimethyl-1-butanol

    Energy Technology Data Exchange (ETDEWEB)

    Massalska-Arodz, Maria [H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland) and Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan)]. E-mail: Maria.Massalska-Arodz@ifj.edu.pl; Nakamoto, Tadahiro [Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan); Wasiutynski, Tadeusz [H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland); Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan); Mayer, Jacek [H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland); Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan); Krawczyk, Jan [H. Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Cracow (Poland); Sorai, Michio [Research Center for Molecular Thermodynamics, Graduate School of Science, Osaka University, Toyonaka, Osaka, 560-0043 (Japan)]. E-mail: sorai@chem.sci.osaka-u.ac.jp

    2004-10-01

    As a part of a project for glass-formers having various values of fragility, molecular dynamics of a glass-forming material 3,3-dimethyl-1-butanol has been presented on the basis of the dielectric relaxation studies. Three characteristic relaxations were observed. To provide thermodynamic aspects of this material, adiabatic heat-capacity calorimetry has also been performed in the (13 to 302) K temperature range. The stable crystal of this material melts at T{sub m} = 235.7 K. When the material is rapidly cooled at a rate greater than 5 K min{sup -1}, the liquid is easily super-cooled and eventually transformed to a glassy state. Standard thermodynamic quantities are evaluated for both the stable crystalline and the glassy states. Structural relaxation processes are discussed in relation to the phase behaviour revealed by the calorimetry.

  15. Short-Time Beta Relaxation in Glass-Forming Liquids Is Cooperative in Nature

    Science.gov (United States)

    Karmakar, Smarajit; Dasgupta, Chandan; Sastry, Srikanth

    2016-02-01

    Temporal relaxation of density fluctuations in supercooled liquids near the glass transition occurs in multiple steps. Using molecular dynamics simulations for three model glass-forming liquids, we show that the short-time β relaxation is cooperative in nature. Using finite-size scaling analysis, we extract a growing length scale associated with beta relaxation from the observed dependence of the beta relaxation time on the system size. We find, in qualitative agreement with the prediction of the inhomogeneous mode coupling theory, that the temperature dependence of this length scale is the same as that of the length scale that describes the spatial heterogeneity of local dynamics in the long-time α -relaxation regime.

  16. Probing heterogeneous dynamics from spatial density correlation in glass-forming liquids

    Science.gov (United States)

    Li, Yan-Wei; Zhu, You-Liang; Sun, Zhao-Yan

    2016-12-01

    We numerically investigate the connection between spatial density correlation and dynamical heterogeneity in glass-forming liquids. We demonstrate that the cluster size defined by the spatial aggregation of densely packed particles (DPPs) can better capture the difference between the dynamics of the Lennard-Jones glass model and the Weeks-Chandler-Andersen truncation model than the commonly used pair correlation functions. More interestingly, we compare the mobility of DPPs and loosely packed particles, and we find that high local density correlates well with slow dynamics in systems with relatively hard repulsive interactions but links to mobile ones in the system with soft repulsive interactions at one relaxation time scale. Our results show clear evidence that the above model dependence behavior stems from the hopping motion of DPPs at the end of the caging stage due to the compressive nature of soft repulsive spheres, which activates the dynamics of DPPs in the α relaxation stage.

  17. Glass forming ability and thermodynamic properties of Ti(Zr,Hf)NiCu shape memory alloys

    Science.gov (United States)

    Pasko, A.; Kolomytsev, V.; Babanly, M.; Sezonenko, A.; Ochin, P.; Portier, R.; Vermaut, Ph.

    2003-10-01

    Rapidly solidified amorphous and crystalline-amorphous ribbons have been produced from a number of quatemary Ti{50+z-x}(Zr,Hf){ x}Ni{50- z-y}Cu{ y} alloys where z =(-5, 0, 5). Structural states were checked by XRD, crystallization behaviour of amorphous phase and martensitic transformations in crystalline material were studied by DSC. The glass transition and crystallization temperatures have been measured at different heating rates, and the crystallization activation energy for each composition and heat event bas been calculated. Isothermal crystallization gives an alternative method of determining the activation energy according to the Arrhenius equation. Contradictory requirements for the conditions of martensitic transformation and good glass forming ability is discussed.

  18. Glass Transitions in Monodisperse Cluster-Forming Ensembles: Vortex Matter in Type-1.5 Superconductors

    Science.gov (United States)

    Díaz-Méndez, Rogelio; Mezzacapo, Fabio; Lechner, Wolfgang; Cinti, Fabio; Babaev, Egor; Pupillo, Guido

    2017-02-01

    At low enough temperatures and high densities, the equilibrium configuration of an ensemble of ultrasoft particles is a self-assembled, ordered, cluster crystal. In the present Letter, we explore the out-of-equilibrium dynamics for a two-dimensional realization, which is relevant to superconducting materials with multiscale intervortex forces. We find that, for small temperatures following a quench, the suppression of the thermally activated particle hopping hinders the ordering. This results in a glass transition for a monodispersed ensemble, for which we derive a microscopic explanation in terms of an "effective polydispersity" induced by multiscale interactions. This demonstrates that a vortex glass can form in clean systems of thin films of "type-1.5" superconductors. An additional setup to study this physics can be layered superconducting systems, where the shape of the effective vortex-vortex interactions can be engineered.

  19. Correlating the stretched-exponential and super-Arrhenius behaviors in the structural relaxation of glass-forming liquids.

    Science.gov (United States)

    Wang, Lianwen; Li, Jiangong; Fecht, Hans-Jörg

    2011-04-20

    Following the report of a single-exponential activation behavior behind the super-Arrhenius structural relaxation of glass-forming liquids in our preceding paper, we find that the non-exponentiality in the structural relaxation of glass-forming liquids is straightforwardly determined by the relaxation time, and could be calculated from the measured relaxation data. Comparisons between the calculated and measured non-exponentialities for typical glass-forming liquids, from fragile to intermediate, convincingly support the present analysis. Hence the origin of the non-exponentiality and its correlation with liquid fragility become clearer.

  20. DEVELOPMENT AND VALIDATION OF UV SPECTROPHOTOMETRIC ESTIMATION OF EBASTINE IN BULK AND TABLET DOSAGE FORM USING AREA UNDER CURVE METHOD

    Directory of Open Access Journals (Sweden)

    Dahivadkar Manish Sudhakar

    2013-06-01

    Full Text Available The aim of this work is to develop a simple, accurate, reproducible and cost effective spectrophotometric method for determination of Ebastine in bulk and pharmaceutical dosage form. This method is basedon area under curve (AUC in wavelength range of 247-257nm and method has followed linearity in the concentration range of 5-30μg/ml. Methanol was used as a solvent. The developed analytical method was validated as per International Conference on Harmonization (ICH guidelines. The value of correlation coefficient (R2 was 0.999. Limit of Detection and Limit of Quantitation were calculated as 0.78µg/ml and 2.37µg/ml, respectively. Results of the recovery studies showed good accuracy of the method. Validation results suggest that the developed method can be used for routine quality control studies for assay of Ebastine in bulk and tablet dosage form.

  1. HEXAHEDRAL ELEMENT REFINEMENT FOR THE PREDICTION-CORRECTION ALE FEM SIMULATION OF 3D BULKING FORMING PROCESS

    Institute of Scientific and Technical Information of China (English)

    J. Chen; Y.X. Wang; W.P. Dong; X.Y. Ruan

    2004-01-01

    Based on the characteristics of 3D bulk forming process, the arbitrary Lagrangian-Eulerian (ALE)formulation-based FEM is studied, and a prediction-correction ALE-based FEM is proposed which integrates the advantages of precisely predicting the boundary configuration of the deformed material, and of efficiently avoiding hexahedron remeshing processes. The key idea of the prediction-correction ALE FEM is elaborated in detail. Accordingly, the strategy of mesh quality control, one of the key enabling techniques for the 3D bulk forming process numerical simulation by the prediction-correction ALE FEM is carefully investigated, and the algorithm for hexahedral element refinement is formulated based on the mesh distortion energy.

  2. Improved plasticity by electropulsing in a Zr{sub 62}Al{sub 19}Ni{sub 19} bulk metallic glass

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, J L; Lu, J X; Shek, C H, E-mail: apchshek@cityu.edu.h [Department of physics and materials science, City University of Hong Kong (Hong Kong)

    2009-01-01

    The present work reported the application of electropulsing technique (EPT) for improving plasticity of a Zr{sub 62}Al{sub 19}Ni{sub 19} bulk metallic glass. After the elecropulsing with a small current of 5A, no obvious crystallization was observed in X-ray diffraction (XRD) patterns. Results of differential scanning calorimetry (DSC) measurements indicated that the glass transition temperature was reduced from 698K to 691K. Room-temperature uniaxial compression tests revealed that the treated BMG showed larger plastic deformation up to 6%, compared with less than 2% plasticity of untreated sample, at a 1x10{sup -4} s{sup -1} strain rate. SEM observation showed that the sample after electropulsing treatment show significant difference in the distribution of shear bands from that of the untreated one.

  3. Effects of femtosecond laser ablation on the surface morphology and microstructure of a bulk TiCuPdZr glass alloy

    Institute of Scientific and Technical Information of China (English)

    WANG Hongshui; LIANG Chunyong; CHEN Xueguang; WANG Lei; YANG Yang; YANG Jianjun; ZHU Shengli; LI Changyi

    2009-01-01

    The effects of femtosecond laser ablation on the surface characteristics and microstructure of a bulk TiCuPdZr glass alloy were investigated. The heat influence zone of femtosecond laser ablated with a laser energy of 100 μJ exhibits a ripple-like feather, while a porous structure appears on the surface of the specimen ablated by a 200 μJ femtosecond laser. The contents of Ti, Zr, and Pd on the ablated surface decrease and that of Cu increases with increasing laser energy. The crystallization process occurs on the glass alloy specimens during femtosecond laser ablation, and the crystallinity of a 100 μJ femtosecond laser-ablated specimen is greater than that of a 200 μJ femtosecond laser-ablated one.

  4. Identification of a Secondary Crystallized Phase formed during Nuclear Glasses Leaching - Effect of the Leached Glass Composition

    Science.gov (United States)

    Thien, Bruno; Godon, Nicole; Frugier, Pierre; Gin, Stéphane; Ayral, André

    2010-05-01

    Silicate glass leaching in a unrenewed aqueous solution leads to gel formation at the glass water interface. This amorphous hydrated layer sometimes behaves like a diffusion barrier: the glass alteration rate decreases according to an inverse square root of time equation. In the case of Mg-containing glasses, the alteration rate usually remains quasi constant and seems to be controlled by the growth of secondary crystallized phases. These phases consume elements from solution. They can sustain gel dissolution inducing a decrease of its passivating properties. Long-term behaviour modelling of Mg-containing glasses designed for the confinement of fission products (AVM glasses, Atelier de vitrification de Marcoule, France) first requires a precise identification of these Mg-rich phases. Experimental investigations were performed on several glass samples using X-ray diffraction (XRD), 27Al and 29Si MAS NMR and elemental chemical analysis. Aluminous hectorite Na0.45(Mg2.28Li0.11Al0.39Fe0.06M0.16)(Si3.21Al0.79)O10(OH)2, with M being a divalent cation, was identified. 25 glasses were required for a full representation in term variations of AVM glasses composition range. Their residual alteration rates were proved to significantly depend on glass composition since a one order of magnitude difference was measured between the less and the most altered glasses. Nevertheless, the same crystallized phase was evidenced whatever the glass composition and whatever the initial composition of the solution (pure water or Mg-rich groundwater). Only a shift of the (060) peak between 1.521 and 1.530 Å was evidenced. It can be attributed to slight composition variations. Relations between the glass magnesium fraction, the amount of precipitated hectorite, the residual rate, and the measured pH are not obvious. However, hectorite precipitation was proved to depend on pH, being favoured between pH50°C 9 and 9.5. Moreover, the higher the amount of precipitated hectorite, the lower the

  5. Evaluation of final waste forms and recommendations for baseline alternatives to group and glass

    Energy Technology Data Exchange (ETDEWEB)

    Bleier, A.

    1997-09-01

    An assessment of final waste forms was made as part of the Federal Facilities Compliance Agreement/Development, Demonstration, Testing, and Evaluation (FFCA/DDT&E) Program because supplemental waste-form technologies are needed for the hazardous, radioactive, and mixed wastes of concern to the Department of Energy and the problematic wastes on the Oak Ridge Reservation. The principal objective was to identify a primary waste-form candidate as an alternative to grout (cement) and glass. The effort principally comprised a literature search, the goal of which was to establish a knowledge base regarding four areas: (1) the waste-form technologies based on grout and glass, (2) candidate alternatives, (3) the wastes that need to be immobilized, and (4) the technical and regulatory constraints on the waste-from technologies. This report serves, in part, to meet this goal. Six families of materials emerged as relevant; inorganic, organic, vitrified, devitrified, ceramic, and metallic matrices. Multiple members of each family were assessed, emphasizing the materials-oriented factors and accounting for the fact that the two most prevalent types of wastes for the FFCA/DDT&E Program are aqueous liquids and inorganic sludges and solids. Presently, no individual matrix is sufficiently developed to permit its immediate implementation as a baseline alternative. Three thermoplastic materials, sulfur-polymer cement (inorganic), bitumen (organic), and polyethylene (organic), are the most technologically developed candidates. Each warrants further study, emphasizing the engineering and economic factors, but each also has limitations that regulate it to a status of short-term alternative. The crystallinity and flexible processing of sulfur provide sulfur-polymer cement with the highest potential for short-term success via encapsulation. Long-term immobilization demands chemical stabilization, which the thermoplastic matrices do not offer. Among the properties of the remaining

  6. Effect of local structures on crystallization in deeply undercooled metallic glass-forming liquids

    Science.gov (United States)

    Jiang, S. Q.; Wu, Z. W.; Li, M. Z.

    2016-04-01

    The crystallization mechanism in deeply undercooled ZrCu metallic glass-forming liquids was investigated via molecular dynamics simulations. It was found that the crystallization process is mainly controlled by the growth of crystal nuclei formed by the BCC-like atomic clusters, consistent with experimental speculations. The crystallization rate is found to relate to the number of growing crystal nuclei in the crystallization process. The crystallization rate in systems with more crystal nuclei is significantly hindered by the larger surface fractions of crystal nuclei and their different crystalline orientations. It is further revealed that in the crystallization in deeply undercooled regions, the BCC-like crystal nuclei are formed from the inside of the precursors formed by the FCC-like atomic clusters, and growing at the expense of the precursors. Meanwhile, the precursors are expanding at the expense of the outside atomic clusters. This process is consistent with the so-called Ostwald step rule. The atomic structures of metallic glasses are found to have significant impact on the subsequent crystallization process. In the Zr85Cu15 system, the stronger spatial correlation of Cu atoms could hinder the crystallization processes in deeply undercooled regions.

  7. Influence of the irradiation temperature on the surface structure and physical/chemical properties of Ar ion-irradiated bulk metallic glasses

    Energy Technology Data Exchange (ETDEWEB)

    Menéndez, E., E-mail: Enric.MenendezDalmau@fys.kuleuven.be [KU Leuven, Instituut voor Kern-en Stralingsfysica, Celestijnenlaan 200 D, 3001 Leuven (Belgium); Hynowska, A.; Fornell, J.; Suriñach, S. [Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Montserrat, J. [Institut de Microelectrònica de Barcelona (IMB-CNM), CSIC, Campus Universitat Autònoma Barcelona, E-08193 Bellaterra (Spain); Temst, K.; Vantomme, A. [KU Leuven, Instituut voor Kern-en Stralingsfysica, Celestijnenlaan 200 D, 3001 Leuven (Belgium); Baró, M.D. [Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); García-Lecina, E. [Surfaces Division, IK4-CIDETEC, Parque Tecnológico de San Sebastián, E-20009 Donostia (Spain); Pellicer, E., E-mail: Eva.Pellicer@uab.cat [Departament de Física, Facultat de Ciències, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain); Sort, J., E-mail: Jordi.Sort@uab.cat [Institució Catalana de Recerca i Estudis Avançats (ICREA) and Departament de Física, Universitat Autònoma de Barcelona, E-08193 Bellaterra (Spain)

    2014-10-15

    Highlights: • Ion irradiation is performed on bulk metallic glasses at 300 K and close to T{sub g}. • Nanocrystallization is observed after high-temperature irradiation. • The mechanical properties are enhanced after the irradiation procedures. • Corrosion resistance is improved after irradiation close to T{sub g}. - Abstract: Surface treatments using multiple Ar ion irradiation processes with a maximum energy and fluence of 200 keV and 1 × 10{sup 16} ions/cm{sup 2}, respectively, have been performed on two different metallic glasses: Zr{sub 55}Cu{sub 28}Al{sub 10}Ni{sub 7} and Ti{sub 40}Zr{sub 10}Cu{sub 38}Pd{sub 12}. Analogous irradiation procedures have been carried out at room temperature (RT) and at T = 620 K (≈0.9 T{sub g}, where T{sub g} denotes the glass transition). The structure, mechanical behavior, wettability and corrosion resistance of the irradiated alloys have been compared with the properties of the as-cast and annealed (T = 620 K) non-irradiated specimens. While ion irradiation at RT does not significantly alter the amorphous structure of the alloys, ion irradiation close to T{sub g} promotes decomposition/nanocrystallization. Consequently, the hardness (H) and reduced Young’s modulus (E{sub r}) decrease after irradiation at RT but they both increase after irradiation at 620 K. While annealing close to T{sub g} increases the hydrophobicity of the samples, irradiation induces virtually no changes in the contact angle when comparing with the as-cast state. Concerning the corrosion resistance, although not much effect is found after irradiation at RT, an improvement is observed after irradiation at 620 K, particularly for the Ti-based alloy. These results are of practical interest in order to engineer appropriate surface treatments based on ion irradiation, aimed at specific functional applications of bulk metallic glasses.

  8. Enhancing plasticity of Zr46.75Ti8.25Cu7.5Ni10Be27.5 bulk metallic glass by precompression

    Science.gov (United States)

    Zhang, J. L.; Yu, H. B.; Lu, J. X.; Bai, H. Y.; Shek, C. H.

    2009-08-01

    Precompression treatments on Zr46.75Ti8.25Cu7.5Ni10Be27.5 bulk metallic glass rods with tapered ends induced controllable stress distributions and resulted in residual stress accompanied with a few tiny shear bands after unloading. The built-in stress state increased macroscopic plasticity dramatically and produced predictable distributions of shear bands in the cylindrical samples cut from the taper-ended samples. The macroscopic plasticity was interpreted in terms of the competition among different types of shear bands.

  9. Finemet nanocrystalline soft magnetic alloy: Investigation of glass forming ability, crystallization mechanism, production techniques, magnetic softness and the effect of replacing the main constituents by other elements

    Energy Technology Data Exchange (ETDEWEB)

    Gheiratmand, T.; Hosseini, H.R. Madaah, E-mail: madaah@sharif.ir

    2016-06-15

    Finemet soft magnetic alloy has been in the focus of interest in the last years due to its high saturation magnetization, high permeability and low core loss. The great quantity of papers has been devoted to the study of its structural and magnetic properties, confirms this claim. This paper reviews the different researches performed on Finemet up to now. The criteria that should be satisfied in order to have the high glass forming ability in an alloy and also the techniques applied for production of Finemet ribbons, powders and bulk samples have been explained. In addition, the mechanism of devitrification, nanocrystallization and magnetic softness in this applicable magnetic alloy has been discussed in detail. Finally, the effect of different elements substituted with the main constituents in Finemet has been summarized through the studies on the characterization and magnetic properties of different Finemet-type alloys. - Highlights: • The criteria for getting high glass forming ability in an alloy have been reviewed. • Techniques applied to make Finemet ribbons and bulk samples have been explained. • Mechanism of devitrification and nanocrystallization has been discussed in detail. • The mechanism of magnetic softness in this magnetic alloy has been demonstrated. • The effect of main elements substitution in Finemet has been summarized.

  10. The meaning of the "universal" WLF parameters of glass-forming polymer liquids.

    Science.gov (United States)

    Dudowicz, Jacek; Douglas, Jack F; Freed, Karl F

    2015-01-07

    Although the Williams-Landell-Ferry (WLF) equation for the segmental relaxation time τ(T) of glass-forming materials is one of the most commonly encountered relations in polymer physics, its molecular basis is not well understood. The WLF equation is often claimed to be equivalent to the Vogel-Fulcher-Tammann (VFT) equation, even though the WLF expression for τ(T) contains no explicit dependence on the fragility parameter D of the VFT equation, while the VFT equation lacks any explicit reference to the glass transition temperature Tg, the traditionally chosen reference temperature in the WLF equation. The observed approximate universality of the WLF parameters C1((g)) and C2((g)) implies that τ(T) depends only on T-Tg, a conclusion that seems difficult to reconcile with the VFT equation where the fragility parameter D largely governs the magnitude of τ(T). The current paper addresses these apparent inconsistencies by first evaluating the macroscopic WLF parameters C1((g)) and C2((g)) from the generalized entropy theory of glass-formation and then by determining the dependence of C1((g)) and C2((g)) on the microscopic molecular parameters (including the strength of the cohesive molecular interactions and the degree of chain stiffness) and on the molar mass of the polymer. Attention in these calculations is restricted to the temperature range (Tg < T < Tg + 100 K), where both the WLF and VFT equations apply.

  11. Influence of the bulk diffusion of rubidium and sodium atoms in glass on their surface dwell time

    Science.gov (United States)

    Atutov, S. N.; Benimetskii, F. A.; Makarov, A. O.

    2017-05-01

    This paper presents the results of measurement of the surface potential and the dwell time of Rb and Na atoms on the surface of S-52 molybdenum glass. It is found that at temperatures below the glass transition temperature, the temperature dependence of the dwell time of Rb atoms is well described by the Arrhenius formula. The surface potentials for Rb and Na are measured to be 0.67 and 1.37 eV, respectively. At temperatures above the glass transition temperature, the dwell time of these atoms increases abnormally. The reason for this is that during impact of an atom on the surface of molten glass, it can penetrate into the volume of the window and then return by diffusion and desorb from the surface. In this case, the dwell time of the atom on the glass is determined by the diffusion time and can be very significant, despite the relatively low potential barrier at the surface and high temperature.

  12. Glass-forming property of hydroxyectoine is the cause of its superior function as a desiccation protectant

    OpenAIRE

    Erwin Arno Galinski; Christoph eTanne; Andrea eMeffert; Golovina, Elena A; Hoekstra, Folkert A.

    2014-01-01

    We were able to demonstrate that hydroxyectoine, in contrast to ectoine, is a good glass-forming compound. Fourier transform infrared (FTIR) and spin label electron spin resonance (ESR) studies of dry ectoine and hydroxyectoine have shown that the superior glass-forming properties of hydroxyectoine result from stronger intermolecular H-bonds with the OH group of hydroxyectoine. Spin probe experiments have also shown that better molecular immobilization in dry hydroxyectoine provides better re...

  13. A New Approach for Handling of Micro Parts in Bulk Metal Forming

    DEFF Research Database (Denmark)

    Mahshid, Rasoul; Hansen, Hans Nørgaard; Arentoft, M.

    2012-01-01

    During last 10 years a lot of research has been done in micro forming processes. In spite of the challenges micro forming has in process, material properties, tooling technology and machines, micro forming technology yields remarkable accuracy and good mechanical properties with high rate...... of production [1]. This can fulfill the demands for mass production and miniaturization in industries and academic communities. According to the recent studies, topics related to materials, process and simulation have been investigated intensively and well documented. Machines, forming tools and handling...... systems are critical elements to complete micro forming technology for transferring knowledge to industries and toward miniature manufacturing systems (micro factory) [2]. Since most metal forming processes are multi stage, making a new handling system with high reliability on accuracy and speed...

  14. Glass waste forms for heat-generating Cs{sup +} and Sr{sup 2+} wastes from pyro-processing

    Energy Technology Data Exchange (ETDEWEB)

    Seo, Min Suk; Heo, Jong [POSTECH, Pohang (Korea, Republic of); Park, Hwan Seo [KAERI, Daejeon (Korea, Republic of)

    2016-05-15

    Pyro-processing is one of the promising recycling technologies for spent nuclear fuel (SNF) from Light Water Reactors (LWR) in Korea. This processing is able to separate radioactive waste nuclei and reduce heat loading in storage site by extraction of heat generating radioactive nuclei. In this study, we used alumino-borosilicate glasses for the immobilization of Cs{sub 2}O and SrO wastes. Glasses were prepared and their important properties including chemical durability were analyzed. In addition, heat generation and its effect on thermal stability of glasses was examined. Glass waste forms that contain heat-generating Cs{sup +} and Sr{sup 2+} from pyro-processing were synthesized. Basic properties of glasses such as densities, linear expansion coefficients and glass-transition temperatures were similar to those of industrial radioactive waste glass. Analysis on the heat load simulation under the failure of the cooling system indicated that maximum temperature inside the canisters are well below the glass-transition temperature of each glass.

  15. Laboratory Testing of Bulk Vitrified Low-Activity Waste Forms to Support the 2005 Integrated Disposal Facility Performance Assessment Erratum

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Gary L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-09-06

    This report refers to or contains Kg values for glasses LAWA44, LAWB45 and LAWC22 affected by calculations errors as identified by Papathanassiu et al. (2011). The corrected Kg values are reported in an erratum included in the revised version of the original report. The revised report can be referenced as follows: Pierce E. M. et al. (2004) Waste Form Release Data Package for the 2005 Integrated Disposal Facility Performance Assessment. PNNL-14805 Rev. 0 Erratum. Pacific Northwest National Laboratory, Richland, WA, USA.

  16. Laboratory Testing of Bulk Vitrified Low-Activity Waste Forms to Support the 2005 Integrated Disposal Facility Performance Assessment. Erratum

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Gary L. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-09-06

    This report refers to or contains Kg values for glasses LAWA44, LAWB45 and LAWC22 affected by calculations errors as identified by Papathanassiu et al. (2011). The corrected Kg values are reported in an erratum included in the revised version of the original report. The revised report can be referenced as follows: Pierce E. M. et al. (2004) Waste Form Release Data Package for the 2005 Integrated Disposal Facility Performance Assessment. PNNL-14805 Rev. 0 Erratum. Pacific Northwest National Laboratory, Richland, WA, USA.

  17. Selection of compositions with high glass forming ability in the Ni-Nb-B alloy system

    Directory of Open Access Journals (Sweden)

    Marcio Andreato Batista Mendes

    2012-10-01

    Full Text Available A combination of an extension of the topological instability "λ criterion" and the "average electronegativity" has been recently reported in the literature to predict compositions with high glass-forming ability (GFA. In the present work, both criteria have been applied to select the Ni61.0Nb36.0B3 alloy with a high glass-forming ability. Ingots were prepared by arc-melting and were used to produce ribbons processed by the melt-spinning technique further characterized by differential scanning calorimetry (DSC, X-ray diffraction (XRD and scanning electron microscopy (SEM. The Ni61.0Nb36.0B3 alloy revealed a complete amorphization and supercooled liquid region ΔTx = 68 K. In addition, wedge-shaped samples were prepared using copper mold casting in order to determine the critical thickness for amorphous formation. Scanning electron microscopy (SEM revealed that fully amorphous samples could be obtained, reaching up to ~800 µm in thickness.

  18. Structure Evolution of Bulk Metallic Glass Zr52.5Ni14.6Al10Cu17.9Ti5 during Annealing

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Bulk metallic glass Zr52.5Ni14.6Al10Cu17.9Ti5 was prepared by melt injection casting method. Its glass transition and crystallization temperatures were determined by differential scanning calorimetry (DSC) to be 631 K and 710 K respectively, By analysis of X-ray diffractometry (XRD) and transmission electron microscopy (TEM), the predominant crystallized phase of Zr2Ni0.67O0.33 distributed on glass state matrix was detected after annealing at 673 K for 600 s. The transformation to Zr2Ni0.67O0.33 and a small amount of ZrAl and Zr2Cu took place after annealing for 600 s at temperature from 703 K to 723 K. With increasing annealing temperature from 753 K to 823 K, the amounts of ZrAl and Zr2Cu increased, but the size of the crystals did not significantly change. The transformation to Zr2Ni0.67O0.33 is interface-controlled, but is diffusion-controlled to Zr2Cu and ZrAl, With increasing annealing temperature up to 200 K above Tx, the nanometer grains became very fine because of the increase of nucleation rate for Zr2Cu and ZrAl.

  19. Using 20-million-year-old amber to test the super-Arrhenius behaviour of glass-forming systems.

    Science.gov (United States)

    Zhao, Jing; Simon, Sindee L; McKenna, Gregory B

    2013-01-01

    Fossil amber offers the opportunity to investigate the dynamics of glass-forming materials far below the nominal glass transition temperature. This is important in the context of classical theory, as well as some new theories that challenge the idea of an 'ideal' glass transition. Here we report results from calorimetric and stress relaxation experiments using a 20-million-year-old Dominican amber. By performing the stress relaxation experiments in a step-wise fashion, we measured the relaxation time at each temperature and, above the fictive temperature of this 20-million-year-old glass, this is an upper bound to the equilibrium relaxation time. The results deviate dramatically from the expectation of classical theory and are consistent with some modern ideas, in which the diverging timescale signature of complex fluids disappears below the glass transition temperature.

  20. Confocal Raman spectroscopy of island nuclei formed at the initial stage of quartz glass crystallization

    Science.gov (United States)

    Pankin, D. V.; Zolotarev, V. M.; Colas, M.; Cornette, J.; Evdokimova, M. G.

    2016-12-01

    Island nuclei formed on a polished quartz-glass surface upon heating to 1100°C have been investigated by confocal Raman spectroscopy. The structural and chemical composition of islands is shown to be a central nucleus, a shell around the nucleus, and a thin peripheral ring closing this shell. The formation and growth of individual regions of an island nucleus are found to occur in several stages. The shell around the nucleus is mainly formed by α-SiO2 and α-cristobalite nanoparticles with a size ≥40 nm, whereas the α-SiO2 nanoparticles in the nucleus and peripheral ring are 2-15 nm in size.