Evaluation of a Characteristic Temperature in the Relaxation of Metallic Glass Forming Liquids

2018 ◽  
Vol 941 ◽  
pp. 2331-2336 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Metallic Glass ◽  
Bond Strength ◽  
Temperature Dependence ◽  
Coordination Number ◽  
Structural Relaxation ◽  
Characteristic Temperature ◽  
Glass Forming ◽  
Metallic Liquids

The high-temperature viscosity of metallic glass-forming liquids is investigated by using the Bond Strength-Coordination Number Fluctuation (BSCNF) model developed by the authors. For many glass-forming liquids, a salient change in the structural relaxation is observed above the melting point. The temperature dependence of the structural relaxation exhibits a deviation from an Arrhenius-like behavior, and upon cooling it transforms to a non-Arrhenius-like one. In the present study, we show that the BSCNF model describes well the high-temperature viscosity behaviors of metallic liquids. The analysis based on the BSCNF model also enables to extract a characteristic temperature at high temperature. The results of the present study show that such characteristic temperature can be a good indicator for the evaluation of the range of the transition from the Arrhenius-like to the non-Arrhenius-like relaxation behavior.

Analysis of Cooperativity in Metallic Glass Forming Liquids

2014 ◽  
Vol 783-786 ◽  
pp. 1889-1894 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda
Keyword(s):  
Metallic Glass ◽  
Bond Strength ◽  
Temperature Dependence ◽  
Coordination Number ◽  
Atomic Motion ◽  
Structural Units ◽  
Mean Values ◽  
Glass Forming ◽  
The Mean ◽  
Fluctuation Model

The relation between fragility and cooperativity of atomic motion in bulk metallic glass forming liquids is studied based on the bond strength-coordination number fluctuation model. The model describes the temperature dependence of the viscosity in terms of the mean values of the bond strength, coordination number and their fluctuations of the structural units that form the melt. According to the model, the cooperativity increases with the increase of fragility. The model estimates that the magnitude of the cooperativityNBextends approximately from 7 to 60 structural units, depending on the material. The temperature dependence ofNBfor different metallic glass forming systems reveals thatNBincreases with the decrease of temperature. The relation betweenNBand diffusivity of atoms is discussed briefly.

Strong Liquid Behavior of Zr-Ti-Cu-Ni-Be Bulk Metallic Glass Forming Alloys

1996 ◽  
Vol 455 ◽  
Author(s):  
Ralf Busch ◽  
Andreas Masuhr ◽  
Eric Bakke ◽  
William L. Johnson
Keyword(s):  
Glass Transition ◽  
Melting Point ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Supercooled Liquid ◽  
Glass Transition Region ◽  
Glass Forming ◽  
Liquid Behavior ◽  
Metallic Liquids ◽  
Microscopic Origin

ABSTRACTThe viscosities of the Zr46.75Ti8.25Cu7.5Ni10Be27.5 and the Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass forming liquids was determined from the melting point down to the glass transition in the entire temperature range of the supercooled liquid. The temperature dependence of the viscosity in the supercooled liquid obeys the Vogel-Fulcher-Tammann (VFT) relation. The fragility index D is about 20 for both alloys and the ratio between glass transition temperature and VFT temperature is found to be 1.5. A comparison with other glass forming systems shows that these bulk metallic glass formers are strong liquids comparable to sodium silicate glass. Furthermore, they are the strongest among metallic glass forming liquids. This behavior is a main contributing factor to the glass forming ability since it implicates a higher viscosity from the melting point down to the glass transition compared to other metallic liquids. Thus, the kinetics in the supercooled liquid is sluggish and yields a low critical cooling rate for glass formation. The relaxation behavior in the glass transition region of the alloys is consistent with their strong glassy nature as reflected by a stretching exponent that is close to 0.8. The microscopic origin of the strong liquid behavior of bulk metallic glass formers is discussed.

Fractional Exponent of the Modified Stokes-Einstein Relation in the Metallic Glass-Forming Melt Pd43Cu27Ni10P20

2010 ◽  
Vol 146-147 ◽  
pp. 1463-1468
Author(s):  
Masahiro Ikeda ◽  
Masaru Aniya
Keyword(s):  
Diffusion Coefficient ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bond Strength ◽  
Coordination Number ◽  
Einstein Relation ◽  
Glass Forming ◽  
Highly Correlated

The diffusion coefficient in the metallic glass-forming systems such as Pd-Cu-Ni-P exhibits a marked deviation from the Stokes-Einstein (SE) relation in the proximity of the glass transition temperature. Such a deviation is characterized by the fractional exponent p of the modified SE expression. For the material Pd43Cu27Ni10P20, it has been reported that it takes the value p = 0.75. In this work, it is shown that the value of p is highly correlated with the ratio ED / ENB, where ED and ENB are the activation energies for diffusion coefficient D and cooperativity NB defined by the Bond Strength-Coordination Number Fluctuation (BSCNF) model. The present paper reports that for the metallic glass-forming melt Pd43Cu27Ni10P20, the fractional exponent p can be calculated accurately within the framework of the BSCNF model.

Model Description of the Unusual Temperature Dependence of the Viscosity of Metallic Glass-Forming Liquids

2021 ◽  
Vol 1016 ◽  
pp. 30-35
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda
Keyword(s):  
High Temperature ◽  
Metallic Glass ◽  
Temperature Dependence ◽  
Present Report ◽  
Model Description ◽  
Unusual Behavior ◽  
Glass Forming ◽  
Viscosity Models ◽  
Strong Transition ◽  
Type Of Behavior

The temperature dependence of the viscosity of some metallic glass forming liquids (MGFLs) exhibits an unusual behavior. At high temperature, the temperature dependence is quite weak, whereas at low temperature, the viscosity varies exponentially. Recently, this type of behavior are attracting much attention, because it can be considered as a manifestation of the fragile-to-strong transition. Well known classic viscosity models do not describe such kind of behavior over a wide temperature range. In the present report, it is shown that a modified version of the Bond Strength-Coordination Number Fluctuation (BSCNF) model describes the behavior observed in MGFLs. For the convenience of the readers, a brief review of the BSCNF model is also given.

Viscosity of Metallic Glass Forming Liquids: Analysis Based on Bond Strength-Coordination Number Fluctuations

2010 ◽  
Vol 638-642 ◽  
pp. 1621-1626 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda
Keyword(s):  
Metallic Glass ◽  
Bond Strength ◽  
Viscous Flow ◽  
Coordination Number ◽  
Structural Units ◽  
Mean Values ◽  
Glass Forming ◽  
The Mean

A model that describes the viscous behavior in terms of the mean values of the bond strength, the coordination number, and their fluctuations of the structural units that form the melt has been proposed by one of the authors. In the present study, the viscous behavior of several metallic glass forming systems are analyzed by using the model. From the analysis, microscopic information such as the number of bonds that must be broken to observe the viscous flow is obtained. It is also shown that when the magnitudes of energy and coordination number fluctuations are equal, the behavior of the viscosity described by our model corresponds perfectly to the behavior described by the Vogel-Fulcher-Tammann (VFT) equation.

A Comparative Study of Molecular Motion Cooperativity in Polymeric and Metallic Glass-Forming Liquids

2016 ◽  
Vol 879 ◽  
pp. 151-156 ◽  
Author(s):  
Masaru Aniya ◽  
Masahiro Ikeda ◽  
Sahara
Keyword(s):  
Metallic Glass ◽  
Bond Strength ◽  
Comparative Study ◽  
Coordination Number ◽  
Molecular Motion ◽  
Fragility Index ◽  
Glass Forming ◽  
Cooperative Relaxation ◽  
The Difference ◽  
The Relationship

In order to investigate the relationship between the bonding nature and the cooperative relaxation, a comparative study of the relaxation behavior in polymeric and metallic glass forming systems has been performed based on the Bond Strength–Coordination Number Fluctuation (BSCNF) model developed by the authors. In the present work, we studied the correlations between the fragility m, the Vogel temperature T0, the degree of molecular cooperativity NB, and the Kohlrausch exponent βKWW. The results show that T0 and NB increase, whereas βKWW decreases systematically with the increase of m. Reflecting the difference of the interatomic interactions of the materials considered, the analysis by the present study reveals that the value of NB in ion-conducing polymers is about 5 times larger than that in metallic systems, and for each system, the material dependence of βKWW is clearly seen in the fragility index m and the cooperativity NB.

Viscosity, Relaxation and Crystallization Kinetics In Zr-Ti-Cu-Ni-Be Strong Bulk Metallic Glass Forming Liquids

1998 ◽  
Vol 554 ◽  
Author(s):  
Ralf Busch ◽  
Andreas Masuhr ◽  
Eric Bakke ◽  
T. Andy Waniuk ◽  
William L. Johnson
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Crystallization Kinetics ◽  
Structural Relaxation ◽  
High Viscosity ◽  
Viscosity Data ◽  
Contributing Factors ◽  
Entropy Of Fusion ◽  
Glass Forming ◽  
Metallic Liquids

AbstractThe high thermal stability of bulk metallic glass (BMG) forming liquids in the undercooled state allows for measurements of thermophysical properties in a large time and temperature window. In this contribution, results on viscous flow, relaxation and crystallization of Zr-Ti-Cu- Ni-Be BMG forming alloys are presented. The data are compared with the kinetics of other metallic and non-metallic liquids. BMG formers are relatively strong liquids with melt viscosities that are about three orders of magnitude larger than in pure metals and other alloys. The strong liquid behavior of these alloys is also reflected by a small entropy of fusion and a weak temperature dependence of the thermodynamic functions upon undercooling. The high viscosity and small driving force for crystallization are major contributing factors to the high glass forming ability and low critical cooling rate. The upper portions of experimental timetemperature- transformation diagrams down to the crystallization nose can be described well using the kinetics deduced from the viscosity data. For lower temperature the viscosity can not describe the crystallization kinetics. The time scale for structural relaxation becomes larger than for diffusive hopping processes. Diffusion stays relatively fast, whereas viscosity and structural relaxation time upon undercooling follow a Vogel-Fulcher-Tammann relation.

Structural topological signature of high-temperature non-Arrhenius crossover in metallic glass-forming liquids

2021 ◽  
Vol 200 ◽  
pp. 113926
Author(s):  
Nannan Ren ◽  
Lina Hu ◽  
Bing Wang ◽  
Kaikai Song ◽  
Pengfei Guan
Keyword(s):  
High Temperature ◽  
Metallic Glass ◽  
Glass Forming
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