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.

Strain-rate dependence of hardening and softening in compression of a bulk-metallic glass

2007 ◽  
Vol 22 (10) ◽  
pp. 2655-2658 ◽  
Author(s):  
W.H. Jiang ◽  
F.X. Liu ◽  
F. Jiang ◽  
K.Q. Qiu ◽  
H. Choo ◽  
...  
Keyword(s):  
Flow Stress ◽  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Plastic Flow ◽  
Shear Banding ◽  
Constant Strain Rate ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Plastic Flow Stress

We investigated the effect of strain rate on the plastic-flow stress of a Zr-based bulk-metallic glass in quasistatic compression. The results indicate that the plastic-flow stress is dependent on the strain rate: an increase in the strain rate leads to a decrease in the plastic-flow stress, and vice versa. However, simply loading, unloading, and reloading at a constant strain rate do not change the plastic-flow stress. This strain-rate dependence of the plastic-flow stress may be related to shear-banding operations.

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.

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.

Stress-assisted-electrochemical corrosion of Cu-based bulk metallic glass

2010 ◽  
Vol 25 (3) ◽  
pp. 592-597 ◽  
Author(s):  
Ding Li ◽  
Mimi Yang ◽  
Fuqian Yang ◽  
Peter K. Liaw
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Current Density ◽  
Deformation Zone ◽  
Shear Banding ◽  
Shear Bands ◽  
Electrochemical Corrosion ◽  
Indentation Load ◽  
Localized Deformation ◽  
Load Range

Using the microindentation test, the stress-assisted-electrochemical corrosion of Cu46.25Zr45.25Al7.5Er1 bulk metallic glass (BMG) was studied in a 10 wt% NaCl electrolyte. The microindentation was performed in an indentation load range of 500 to 4000 mN to create shear bands over the deformation zone. Electric current of various densities was passed through the indented BMGs to evaluate the effect of shear bands and localized deformation on the electrochemical corrosion of the BMGs. Surface pits always initiated from the shear-banding zone and the contact edges between the indenter and the BMGs, and the size of the corroded zone grew with the increase in the polarization time, the indentation load, and the current density. Wormlike amorphous whiskers were formed over the corroded zone, and the density of the wormlike whiskers increased with the current density and polarization time.

In situ thermographic observations on the compression behavior of a relaxed Zr-based bulk-metallic glass

2007 ◽  
Vol 22 (2) ◽  
pp. 368-373 ◽  
Author(s):  
W.H. Jiang ◽  
F.X. Liu ◽  
H.H. Liao ◽  
H. Choo ◽  
P.K. Liaw
Keyword(s):  
Plastic Deformation ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
High Strain ◽  
Shear Banding ◽  
Shear Bands ◽  
Infrared Camera ◽  
Flow Shear ◽  
Compression Behavior

Using an infrared camera, the plastic deformation of a relaxed Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 bulk-metallic glass in a moderately high strain rate compression was observed in situ. The specimen exhibits an inhomogeneous deformation, which is manifested by serrated plastic flow, shear banding, and obvious work softening. Shear-banding operations were observed throughout the plastic deformation. Shear-banding operations started before the nominal yielding; shear bands could not block each other, but their interaction seems to accelerate the plastic deformation. A significant increase in the specimen’s temperature was observed due to shear banding.

Deformation and Failure of Zr57Ti5Cu20Ni8Al10 Bulk Metallic Glass Under Quasi-static and Dynamic Compression

2002 ◽  
Vol 17 (6) ◽  
pp. 1441-1445 ◽  
Author(s):  
T. C. Hufnagel ◽  
T. Jiao ◽  
Y. Li ◽  
L-Q. Xing ◽  
K. T. Ramesh
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
High Speed ◽  
Dynamic Compression ◽  
Shear Bands ◽  
Band Formation ◽  
Deformation And Failure ◽  
Dominant Deformation Mechanism ◽  
High Speed Cinematography ◽  
Mechanism Of Failure

We have examined the mechanical behavior of Zr57Ti5Cu20Ni8Al10 bulk metallic glass under uniaxial compression at strain rates from 10−4to 3 × 103 s−1. The failure stress decreases with increasing strain rate, and shear-band formation remains the dominant deformation mechanism. A consideration of basic properties of adiabatic shear bands makes it appear unlikely that shear bands formed under quasi-static loading are adiabatic; in the dynamic case, the time scales of deformation and thermal conduction are similar, indicating that a more sophisticated calculation is required. In the dynamic tests, however, high-speed cinematography reveals evidence that the mechanism of failure involves an adiabatic component.

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.

scholarly journals Characterization of rate-dependent shear behavior of Zr-based bulk metallic glass using shear-punch testing

2006 ◽  
Vol 21 (1) ◽  
pp. 153-160 ◽  
Author(s):  
L.F. Liu ◽  
L.H. Dai ◽  
Y.L. Bai ◽  
B.C. Wei ◽  
J. Eckert
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Shear Banding ◽  
Shear Bands ◽  
Transfer Model ◽  
Free Volume Theory ◽  
Rate Dependent ◽  
Shear Punch ◽  
Shear Punch Testing

In this study, the rate-dependent mechanical behavior of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass was studied using quasi-static and dynamic shear-punch testing at room temperature. The results demonstrate that the shear strength of this alloy is insensitive to the applied strain rate. However, the formation of shear bands and the serrated flow exhibits a significant strain rate effect. The shear banding-induced fracture patterns and the fracture-melting phenomenon were analyzed based on the free volume theory and the energy transfer model.

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