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  • 1
    Electronic Resource
    Electronic Resource
    Acoustic emission during heterogeneous and homogeneous plastic flow of a metallic glass (1997)
    Springer
    Physics of the solid state 39 (1997), S. 787-790 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements have been made of the acoustic emission that occurs during the plastic deformation of metallic glass subjected to various heat treatments. It is shown that for the same temperature and deformation rate it is possible to have either homogeneous flow with no acoustic emission or localized flow accompanied by intense discrete acoustic emission, depending on the preliminary annealing conditions. From an analysis of the experimental results, it is deduced that the nature of the plastic flow of metallic glasses is determined by the structural relaxation rate at the experimental temperature and the conditions of intense structural relaxation, that plastic flow is homogeneous viscoelastic, and, under the conditions of kinetically inhibited structural relaxation, that it is localized and occurs by a dislocation-like mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1129970
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  • 2
    Electronic Resource
    Electronic Resource
    Creep kinetics of linearly heated metallic glasses (1997)
    Springer
    Physics of the solid state 39 (1997), S. 1953-1957 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A quantitative theory of creep in linearly heated metallic glasses is developed in terms of new ideas on the kinetics of irreversible structural relaxation under external mechanical stress. The validity of the resulting flow equation has been confirmed by a specially devised experiment. It is shown that the temperature dependence of Newtonian viscosity is determined by the rate of heating and the energy spectrum of irreversible structural relaxation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130207
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  • 3
    Electronic Resource
    Electronic Resource
    Kinetics of isothermal creep in metallic glasses including the statistical distribution of activation parameters (1997)
    Springer
    Physics of the solid state 39 (1997), S. 1796-1802 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A generalized theoretical model is proposed for the structural relaxation of metallic glasses under load. Structural relaxation is treated as a set of irreversible, uncorrelated, two-stage atomic displacements in some regions of the structure, the “relaxation centers.” In loaded samples structural relaxation acquires a directional character, leading to the buildup of plastic deformation in accordance with the magnitude and orientation of the applied mechanical stress. General equations are obtained for creep kinetics including a continuous statistical distribution of the principal activation parameters. These equations are compared with the results of a special experiment. The model is found to provide an adequate interpretation of the observed creep kinetics, except for the first 101–102 seconds after loading. It is argued that the initial stage of creep is determined by reversible atomic realignments in relaxation centers having symmetric two-well potential.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1130176
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  • 4
    Electronic Resource
    Electronic Resource
    Kinetics of structural relaxation and regularities of plastic flow of metallic glasses (1999)
    Springer
    Physics of the solid state 41 (1999), S. 1989-1994 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract On the basis of a calculation of the structural relaxation rate and an experimental acoustical-emission determination of the temperature of the transition from localized to uniform flow it is argued that the type of plastic deformation of metallic glasses is uniquely determined by the kinetic structure of the relaxation. In the case of a kinetically hindered structural relaxation, which is characteristic for tests of initial samples at temperatures T〈380–420 K, a localized dislocational deformation is realized. At higher temperatures, “memory” of the thermal prehistory of the samples is lost (aging at room temperature), the structural relaxation rate grows abruptly and plastic flow becomes uniform viscoplastic flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1131140
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  • 5
    Electronic Resource
    Electronic Resource
    Non-Newtonian deformation of Co-based metallic glass at low stresses (2000)
    Springer
    Physics of the solid state 42 (2000), S. 697-700 
    Details
    ISSN: 1063-7834
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The results of precision measurements of creep in Co-based metallic glass are presented. It is shown that, in spite of generally accepted concepts, plastic flow at low stresses under intense structural relaxation conditions is of a non-Newtonian type. Consequences of this fact are considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1131273
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  • 6
    Electronic Resource
    Electronic Resource
    The role of structural relaxation in the plastic flow of metallic glasses (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 5724-5731 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The role of structural relaxation in the plastic flow behavior of metallic glasses is analyzed both theoretically and experimentally. The characteristic time of structural relaxation is calculated as a function of glass thermal prehistory. It is revealed that heating above the room temperature by several tens of Kelvins results in a sharp, by several orders of magnitude, decrease of this time. It is argued that localized "inhomogeneous" dislocation-like flow occurs on loading if the characteristic time of structural relaxation is much greater than the characteristic loading time, while "homogeneous" viscous deformation is observed in the opposite case. Precise measurements of acoustic emission in a Co-based metallic glass being loaded at different temperatures and strain rates are employed for verification of this statement. It is shown that the inhomogeneous → homogeneous flow transition occurs at temperatures somewhat higher than T=400 K, and the transition temperature increases by (approximate) 40 K as the strain rate increases by two orders of magnitude. Theoretical estimations show that for the inhomogeneous flow the characteristic time of structural relaxation in the loaded state is indeed much greater than the characteristic loading time. It is concluded that the kinetics of structural relaxation determines the flow mode of metallic glasses in a unique manner. The kinetically "frozen" structural relaxation gives rise to a crystalline-like localized flow under load while intensive structural relaxation facilitates a viscous glass-like behavior. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367428
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  • 7
    Electronic Resource
    Electronic Resource
    On the determination of the crystallization activation energy of metallic glasses (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 8440-8443 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dependence of the crystallization temperature on the heating rate was measured for five conventional melt spun metallic glasses. The results obtained, together with similar data taken from the literature, were analyzed using the Kissinger method. It is shown that application of this method to glass transition and crystallization of metallic glasses leads to unreasonably high apparent attempt frequencies, by many orders of magnitude above the Debye frequency. It is concluded, in accordance with some remarks available in the literature, that this method gives obscure values of the activation parameters of glass transition and crystallization of metallic glasses. A simple equation for approximate estimate of the crystallization onset activation energy of metallic glasses is proposed. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373560
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  • 8
    Electronic Resource
    Electronic Resource
    On the nature of low-temperature anomalies of the anelastic properties of metallic glasses (1997)
    Springer
    Technical physics 42 (1997), S. 1145-1154 
    Details
    ISSN: 1090-6525
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In Memory of A. M. Roshchupkin The low-temperature (30〈T〈300 K) internal friction and elastic modulus of the metallic glass (MG) Ni60Nb40 subjected to preliminary cold working by rolling, high-temperature uniform straining, or electrolytic hydrogenation is investigated. It is established that cold rolling, which induces localized plastic flow, or hydrogenation radically alters the temperature dependences of the internal friction and elastic modulus: hysteresis appears in the background damping and intense relaxational peaks arise in the internal friction, accompanied by a defect of the elastic modulus. A uniform strain does not affect the low-temperature anelastic behavior of MGs. Microplastic deformation is observed to accompany the hydrogenation of weakly loaded samples. It is asserted that localized microplastic deformation also occurs on hydrogenation with no load. Plastic flow accompanying both rolling and hydrogenation occurs by the formation and motion of dislocationlike defects, which in the presence of an external load of alternating sign give rise to the observed anelastic anomalies. It is concluded that the low-temperature internal-friction peaks, described in the literature, in the “as-quenched,” cold-deformed, or hydrogenated MGs are all of a dislocation nature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1134/1.1258811
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