Correlation between fragility and structural relaxation dynamics of bulk metallic glass-forming liquids

2013 ◽  
Vol 551 ◽  
pp. 164-167 ◽  
Author(s):  
M. Zhang
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Structural Relaxation ◽  
Relaxation Dynamics ◽  
Glass Forming

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.

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).

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.

scholarly journals EFFECT OF STRUCTURAL RELAXATION ON THE DEFORMATION BEHAVIOR OF A Zr64.13Cu15.75Ni10.12Al10 BULK METALLIC GLASS UNDER NANOINDENTATION

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2320-2325 ◽  
Author(s):  
JIANSHENG GU ◽  
BINGCHEN WEI ◽  
TAIHUA ZHANG ◽  
YIHUI FENG ◽  
YANPING HU ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Structural Relaxation ◽  
Deformation Behavior ◽  
Isothermal Annealing ◽  
Flow Behavior ◽  
Thermal And Mechanical Properties ◽  
Scanning Calorimetry ◽  
Obvious Effect ◽  
Dsc Curves

Structural relaxation by isothermal annealing below the glass transition temperature is conducted on a Zr 64.13 Cu 15.75 Ni 10.12 Al 10 bulk metallic glass. The effect of structural relaxation on thermal and mechanical properties was investigated by differential scanning calorimetry and instrumented nanoindentation. The recovery of the enthalpy in the DSC curves indicates that thermally unstable defects were annihilated through structural relaxation. During nanoindentation, the structural relaxation did not have a significant influence on the serrated plastic flow behavior. However, Structural relaxation shows an obvious effect in increasing both the hardness and elastic modulus, which is attributed to the annihilation of thermally unstable defects that resulted from the relaxation.

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