Tension and stress relaxation behavior of a La-based bulk metallic glass

2007 ◽  
Vol 22 (12) ◽  
pp. 3303-3308 ◽  
Author(s):  
G.Q. Zhang ◽  
Q.K. Jiang ◽  
X.P. Nie ◽  
L.Y. Chen ◽  
L.N. Wang ◽  
...  
Keyword(s):  
Glass Transition ◽  
Stress Relaxation ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Annealing Time ◽  
Fracture Morphology ◽  
Cast Sample ◽  
Brittle Behavior ◽  
Tension Tests

Tension and stress-relaxation behaviors of a La62Al14Cu11.7Ag2.3Ni5Co5 bulk metallic glass (BMG) as a function of isothermal annealing time have been investigated. It is found that annealing at 373 K below the glass-transition temperature (423 K) of the BMG alloy causes an increase of special heat difference at the glass transition and density of the alloy, indicating a reduction of free volume in the BMG alloy with annealing time. Compared with the as-cast sample, the fracture strength, Vickers hardness, viscosity, Young’s modulus, and stress-relaxation stability of the annealed BMGs increase with annealing time, which is caused by the reduction of free volume in the annealed samples. Furthermore, a change of fracture morphology from a mixture of smooth and furrow zones in the as-cast sample to a mainly furrow zone in the sample annealed for 8 h was also observed. All samples exhibit brittle behavior during tension tests.

Free Volume Evolution in Bulk Metallic Glass during High Temperature Creep

2002 ◽  
Vol 754 ◽  
Author(s):  
B. S. Sundar Daniel ◽  
Martin Heilmaier ◽  
Birgit Bartusch ◽  
Jörn Kanzow ◽  
Katja Günther-Schade ◽  
...  
Keyword(s):  
Glass Transition ◽  
Plastic Strain ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Metallic Glasses ◽  
Constant Strain Rate ◽  
Dsc Analysis ◽  
Scanning Calorimetry ◽  
Positron Lifetime Spectroscopy

ABSTRACTMetallic glasses lack long-range translational symmetry and have excess volume trapped within their amorphous structure, which has a direct bearing on their physical properties including deformation characteristics. Moreover, the trapped excess free volume is directly correlated to the defect concentration facilitating the possibility to model the temperature and time dependence of the free volume changes during creep as a trade off between defect generation and annihilation. Using differential scanning calorimetry (DSC) analysis the residual free volume of a metallic glass can be characterised based on the glass transition peak height (Δcp). In the present work constant strain rate tests were carried out at the ‘onset’ (Tgon = 685 K) and ‘point of inflection’ (Tgp = 705 K) of the calorimetric glass transition to study the time dependent flow behaviour in Zr55Cu30Al10Ni5 bulk metallic glass. Modelling based on DSC analysis and positron lifetime spectroscopy on samples creep deformed to different plastic strain values corroborate the stress decrease after the peak stress (‘stress overshoot’) occurring in bulk metallic glasses with increasing plastic strain to be associated with a small increase in free volume.

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.

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.

Effect of high pressure on glass transition in Zr-Ti-Cu-Ni-Be bulk metallic glass

2002 ◽  
Vol 754 ◽  
Author(s):  
Wei Hua Wang ◽  
Ping Wen ◽  
Yan Hui Zhao ◽  
Ming Xiang Pan ◽  
De Qian Zhao
Keyword(s):  
High Pressure ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Bulk Glass ◽  
Free Volume Theory ◽  
Glass Forming

ABSTRACTA new method is developed to directly exhibit glass transition in Zr-Ti-Cu-Ni-Be bulk glass-forming alloy under high pressure in metallic glass. Via the method, we derive an increase of glass transition temperature, Tg with pressure of 5.6 K/GPa, and a formation volume (ΔVf) of 6.5 Å3 for diffusion and the migration volume (ΔVm) of 6.5 Å3. The glass transition under high pressure is simulated based on the free-volume theory, and the simulations are consistent with the experimental observations.

Free Volume Changes and Crack Tip Deformation in Bulk Metallic Glass Alloys and their Composites

2003 ◽  
Vol 806 ◽  
Author(s):  
Biraja P. Kanungo ◽  
Matthew J. Lambert ◽  
Katharine M. Flores
Keyword(s):  
Glass Transition ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Metallic Glasses ◽  
Structural Relaxation ◽  
Strain Localization ◽  
Shear Bands ◽  
Inhomogeneous Deformation ◽  
Volume Changes

ABSTRACTThe free volume changes associated with deformation of metallic glasses play an important role in strain localization in shear bands. However the details of these structural changes during inhomogeneous deformation are unclear. In this study, the free volume changes in Cu60Zr30Ti10 and Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glasses were examined and quantified using differential scanning calorimetry following rolling and low temperature annealing. It was found that the height of the endothermic peak associated with the glass transition decreased following deformation whereas annealing resulted in an increase in the peak height. Additionally, the exothermic event associated with structural relaxation prior to the glass transition occurred at a lower temperature after rolling in the Zr-based system. Surprisingly, a similar shift in the onset temperature was not observed in the Cu-based system, suggesting a different structural relaxation mechanism. The Zr-based system was successfully modeled and the results indicated that the free volume increased ∼4% with inhomogeneous deformation and decreased ∼14% with annealing, consistent with expectations. In an effort to further characterize strain localization in shear bands, the development of a crack tip damage zone in a Zr-based bulk metallic glass composite was studied using scanning electron and atomic force microscopy. The first shear band developed at an angle of ∼60° from the crack propagation direction. This is discussed in light of the Mohr-Coulomb yield criterion for metallic glasses. The reinforcement phase arrested the growth of individual shear bands, while accumulated damage resulted in the shear bands cutting through the crystalline phase, ultimately resulting in crack branching and failure.

Strain, Stress and Stress Relaxation in Oxidized Zrcual-Based Bulk Metallic Glass

2020 ◽  
Author(s):  
Saber Haratian ◽  
Frank Niessen ◽  
Flemming B. Grumsen ◽  
Mitchell J. B. Nancarrow ◽  
Elena Pereloma ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Strain Stress

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.

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