scholarly journals Formation and dilatation of shear bands in a Cu-Zr metallic glass: A free volume perspective

2016 ◽  
Vol 120 (23) ◽  
pp. 235101 ◽  
Author(s):  
Chunguang Tang ◽  
Hailong Peng ◽  
Yu Chen ◽  
Michael Ferry
Keyword(s):  
Metallic Glass ◽  
Free Volume ◽  
Shear Bands

Effect of Structure Relaxation on the Plastic Deformation Behaviour in a Zr-Based BMG under Indenter

2009 ◽  
Vol 618-619 ◽  
pp. 437-441
Author(s):  
Hao Wen Xie ◽  
Peter D. Hodgson ◽  
Cui E Wen
Keyword(s):  
Plastic Deformation ◽  
Shear Band ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Cast Alloy ◽  
Deformation Behaviour ◽  
Shear Bands ◽  
Structure Relaxation ◽  
Effect Of Structure

Vickers and nano indentations were performed on a structurally relaxed Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass (BMG), and the evolution of the shear bands in the relaxed BMG was investigated and compared to that in the as-cast alloy. Results indicate that the plastic deformation in the BMG with structure relaxation is accommodated by the semicircular (primary) and radial (secondary) as well as tertiary shear bands. Quantitatively, the shear band density in the relaxed alloy was much lower than that in the as-cast alloy. The annihilation of free volume caused by the annealing was responsible for the embrittlement of the sample with structure relaxation.

Plastic flow in dynamic compression of a Zr-based bulk metallic glass

2006 ◽  
Vol 21 (6) ◽  
pp. 1570-1575 ◽  
Author(s):  
W.H. Jiang ◽  
F.X. Liu ◽  
D.C. Qiao ◽  
H. Choo ◽  
P.K. Liaw
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Plastic Flow ◽  
Dynamic Compression ◽  
Maximum Shear Stress ◽  
Shear Banding ◽  
Shear Bands ◽  
Free Volume Model ◽  
Geometrically Constrained

Using geometrically constrained specimens, the plastic flow behaviors of the as-cast and the relaxed Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 bulk metallic glass in the dynamic compression were investigated. Both alloys exhibit a significant plasticity in the dynamic compression. The plastic deformation in both alloys is still inhomogeneous, which is characterized by the serrated plastic flow and the formation of shear bands. Free volumes affect the shear banding and the plastic flow. The reduced free volume results in the deviation of the shear banding direction from the maximum shear stress. The relaxed alloy exhibits the obvious stress overshoot, which is consistent with the theoretical prediction using a free volume model.

scholarly journals Free-volume dependent pressure sensitivity of Zr-based bulk metallic glass

2009 ◽  
Vol 24 (8) ◽  
pp. 2697-2704 ◽  
Author(s):  
Alban Dubach ◽  
K. Eswar Prasad ◽  
Rejin Raghavan ◽  
Jorg F. Löffler ◽  
Johann Michler ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Structural State ◽  
Shear Bands ◽  
Compressive Yield Strength ◽  
Pressure Sensitivity ◽  
Constraint Factor ◽  
Shear Transformation Zones

Instrumented indentation experiments on a Zr-based bulk metallic glass (BMG) in as-cast, shot-peened and structurally relaxed conditions were conducted to examine the dependence of plastic deformation on its structural state. Results show significant differences in hardness, H, with structural relaxation increasing it and shot peening markedly reducing it, and slightly changed morphology of shear bands around the indents. This effect is in contrast to uniaxial compressive yield strength, σy, which remains invariant with the change in the structural state of the alloys investigated. The plastic constraint factor, C = H/σy, of the relaxed BMG increases compared with that of the as-cast glass, indicating enhanced pressure sensitivity upon annealing. In contrast, C of the shot-peened layer was found to be similar to that observed in crystalline metals, indicating that severe plastic deformation could eliminate pressure sensitivity. Microscopic origins for this result, in terms of shear transformation zones and free volume, are discussed.

scholarly journals Notch Effect on Plastic Deformation of Metallic Glass: A Numerical Study by Revised Free-Volume Theory

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
J. F. Yan ◽  
W. J. Meng ◽  
Z. Chen ◽  
H. Guo ◽  
X. G. Yan
Keyword(s):  
Metallic Glass ◽  
Free Volume ◽  
Numerical Study ◽  
Shear Bands ◽  
Notch Effect ◽  
Volume Distribution ◽  
Free Volume Theory ◽  
Tension And Compression ◽  
Strength Asymmetry ◽  
Strength And Plasticity

By means of a revised free-volume theory, the notch effect on metallic glass was systematically investigated by the numerical method. Simulations on specimens without notches demonstrated that the parameters being determined in this work could reasonably describe the strength asymmetry of tension and compression. Moreover, four samples with different notches were used to numerically investigate the notch effect on global strength and plasticity. A better agreement could also be achieved between current simulations with existing experimental results, compared with another free-volume model. Combined with the free-volume distribution during deformation process, it was proven that the intersection of two major shear bands is the cause for the strength and plasticity enhancement found in sample with two symmetric notches. Besides, strength asymmetry between tension and compression was also found for notched samples. Compressive strengths are accordingly higher than tensile ones. Moreover, with the augment of the aspect ratio, the plasticity for specimens with two symmetric notches was found to increase firstly and then decrease afterwards.

Plastic Deformation and Mechanical Softening of Pd40Cu30Ni10P20 Bulk Metallic Glass During Nanoindentation

2005 ◽  
Vol 20 (10) ◽  
pp. 2719-2725 ◽  
Author(s):  
A. Concustell ◽  
J. Sort ◽  
G. Alcalá ◽  
S. Mato ◽  
A. Gebert ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Loading Rate ◽  
Shear Bands ◽  
Control Mode ◽  
Displacement Control ◽  
Softening Effect ◽  
Wide Range

Nanoindentation tests of Pd40Cu30Ni10P20 bulk metallic glass were performed over a wide range of indentation rates (from 0.04 up to 6.4 mN s−1) under the standard load control mode. New results using the feedback displacement control mode are also presented. The dependence of the pop-in formation on the loading rate is investigated. Variations in hardness and reduced elastic modulus as a function of the indentation rate are observed. A softening effect occurs when increasing the loading rate. This is explained by the differences in plastic deformation achieved at different indentation rates. The displacement control mode was used to avoid the shear localization of the free volume, leading to the almost complete absence of pop-ins along the loading curve. The obtained results suggest that plastic flow in bulk metallic glasses is governed by the rate of creation of free volume, which depends on the strain rate and its localization into shear bands.

Free volume coalescence and void formation in shear bands in metallic glass

2003 ◽  
Vol 93 (3) ◽  
pp. 1432-1437 ◽  
Author(s):  
Wendelin J. Wright ◽  
T. C. Hufnagel ◽  
W. D. Nix
Keyword(s):  
Metallic Glass ◽  
Free Volume ◽  
Shear Bands ◽  
Void Formation

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.

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