Comments on “Mechanical relaxation time scales in a Zr-Ti-Ni-Cu-Be bulk metallic glass” by Daewoong Suh and Reinhold H. Dauskardt [J. Mater. Res. 17, 1254 (2002)]

2003 ◽  
Vol 18 (8) ◽  
pp. 1998-1999 ◽  
Author(s):  
K. Schröter
Keyword(s):  
Relaxation Time ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Stress Relaxation ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Time Scales ◽  
Mechanical Relaxation ◽  
Viscoelastic Relaxation

The stress relaxation results below the glass-transition temperatureTgare a continuation of the viscoelastic relaxation aboveTg. This means that the dynamic glass transition and not a secondary relaxation is the reason for the observed effects.

Mechanical Relaxation Time Scales in a Zr–Ti–Ni–Cu–Be Bulk Metallic Glass

2002 ◽  
Vol 17 (6) ◽  
pp. 1254-1257 ◽  
Author(s):  
Daewoong Suh ◽  
Reinhold H. Dauskardt
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Time Scales ◽  
Mechanical Relaxation ◽  
Viscoelastic Relaxation ◽  
Structural Units ◽  
Commercial Grade ◽  
Calorimetric Studies

The relaxation time scales in a commercial-grade Zr41.25Ti13.75Ni10Cu12.5Be22.5 (at.%) bulk metallic glass were examined using transient and dynamic mechanical experiments. The viscoelastic and sub-Tg relaxations were well described by the Kohlrausch–Williams–Watts relaxation function. A large activation energy (4.0 eV) and small nonexponentiality parameter (approximately 0.5) were observed for viscoelastic relaxation above Tg consistent with the cooperative nature of atomic movements leading ultimately to viscous flow. Conversely, a small activation energy (0.1 eV) and large nonexponentiality parameter (approximately 0.9) were observed for the sub-Tg relaxation suggesting localized atomic adjustments which may involve different structural units or mechanisms. The glass transition was manifested as a decoupling of the sub-Tg and viscoelastic relaxation. The resulting transition temperature determined at a selected time scale was in agreement with the value obtained from calorimetric studies.

Thermodynamic and kinetic fragilities of Mg-based bulk metallic glass-forming liquids

2008 ◽  
Vol 23 (10) ◽  
pp. 2816-2820 ◽  
Author(s):  
H. Ma ◽  
H-J. Fecht
Keyword(s):  
Relaxation Time ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Temperature Dependence ◽  
Bulk Metallic Glass ◽  
Excess Entropy ◽  
Gibbs Equation ◽  
Glass Forming

The thermodynamic and kinetic fragilities of two near-eutectic Mg-based bulk metallic glass (BMG)-forming liquids, Mg61Cu28Gd11 and Mg59.5Cu22.9Ag6.6Gd11, were investigated using high-precision differential scanning calorimeter (DSC). The thermodynamic fragility denoted as F3/4 was determined by evaluating the temperature dependence of the excess entropy Sex. The heating rate dependence of the relaxation time at the glass transition temperature was investigated to measure the kinetic fragility. A positive correlation between the thermodynamic and kinetic fragilities could be established in Mg-based BMG-forming liquids on the basis of Adam-Gibbs equation in contrast to a number of other BMGs.

scholarly journals Effects of Annealing on Enthalpy Recovery and Nanomechanical Behaviors of a La-Based Bulk Metallic Glass

Metals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 579
Author(s):  
Ting Shi ◽  
Lanping Huang ◽  
Song Li
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Structural Relaxation ◽  
Supercooled Liquid ◽  
Supercooled Liquid Region ◽  
Liquid Region ◽  
Nanoindentation Measurement

Structural relaxation and nanomechanical behaviors of La65Al14Ni5Co5Cu9.2Ag1.8 bulk metallic glass (BMG) with a low glass transition temperature during annealing have been investigated by calorimetry and nanoindentation measurement. The enthalpy release of this metallic glass is deduced by annealing near glass transition. When annealed below glass transition temperature for 5 min, the recovered enthalpy increases with annealing temperature and reaches the maximum value at 403 K. After annealed in supercooled liquid region, the recovered enthalpy obviously decreases. For a given annealing at 393 K, the relaxation behaviors of La-based BMG can be well described by the Kohlrausch-Williams-Watts (KWW) function. The hardness, Young’s modulus, and serrated flow are sensitive to structural relaxation of this metallic glass, which can be well explained by the theory of solid-like region and liquid-like region. The decrease of ductility and the enhancement of homogeneity can be ascribed to the transformation from liquid-like region into solid-like region and the reduction of the shear transition zone (STZ).

scholarly journals Stability of ZrTiCuNiBe Bulk Metallic Glass upon Isothermal Annealing Near the Glass Transition Temperature

2002 ◽  
Vol 17 (6) ◽  
pp. 1385-1389 ◽  
Author(s):  
Wei Hua Wang ◽  
Ru Ju Wang ◽  
W. T. Yang ◽  
B. C. Wei ◽  
P. Wen ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Isothermal Annealing ◽  
Scanning Calorimetry ◽  
The Stability ◽  
Property Changes ◽  
Overlap Method

The stability of Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG) upon isothermal annealing near the glass transition temperature has been investigated by using x-ray diffraction, differential scanning calorimetry, and the pulse echo overlap method. The density, elastic constants, and thermodynamic parameters as well as their annealing time dependence have been determined. The microstructural and properties changes of the annealed BMG were checked by acoustic measurement. Obvious structural and property changes were observed with prolonged annealing of the BMG near the glass transition temperature.

scholarly journals Structural Features of the Extraordinary Low Glass Transition Temperature for Au65Cu18Si17 Bulk Metallic Glass

2013 ◽  
Vol 54 (8) ◽  
pp. 1351-1355 ◽  
Author(s):  
Makoto Matsuura ◽  
Wei Zhang ◽  
Shinichi Yamaura ◽  
Takashi Fujita ◽  
Koji Ohara ◽  
...  
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Structural Features

Influence of Structural Relaxation on Compressive Plasticity of Zr64.13Cu15.75Ni10.12Al10 Bulk Metallic Glass

2014 ◽  
Vol 910 ◽  
pp. 48-52 ◽  
Author(s):  
Jian Sheng Gu ◽  
Hui Feng Bo
Keyword(s):  
Differential Scanning Calorimetry ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Structural Relaxation ◽  
Isothermal Annealing ◽  
Scanning Calorimetry

Structural relaxation through isothermal annealing below the glass transition temperature was conducted on a Zr64.13Cu15.75Ni10.12Al10bulk metallic glass. Differential scanning calorimetry was used to quantify enthalpy differences between the as-cast and relaxed samples, which were then related to average free volume differences. The influence of structural relaxation on plasticity was examined. While the free volume decreasement can be clearly observed between the as-cast and relaxed samples, structural relaxation is not accompanied by severe embrittlement.

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