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.

Numerical Determination of Critical Configuration for Mechanical Properties of Metallic Glasses with Notches

2021 ◽  
Vol 13 (2) ◽  
pp. 235-244
Author(s):  
J. F. Yan ◽  
W. J. Meng ◽  
Z. Chen ◽  
H. Guo ◽  
X. G. Yan
Keyword(s):  
Mechanical Properties ◽  
Metallic Glass ◽  
Free Volume ◽  
Numerical Study ◽  
Uniform Elongation ◽  
Shear Banding ◽  
Volume Distribution ◽  
Geometrical Configuration ◽  
Free Volume Theory ◽  
Critical Configuration

A numerical study based on a revised free-volume theory was carried out to determine the critical configuration for mechanical properties in metallic glass with notches. Firstly, parameters being used in constitutive laws were developed and validated to quantitatively describe the asymmetry of tension and compression. Then, systematical simulations under compressive loadings were performed on samples where different horizontal width and vertical distance of two adjacent notches were designed. Engineering stress-strain curves, global strength and uniform elongation were plotted against individual geometrical configuration. Analyses were carried out to reveal the shear banding process of different samples by means of free-volume distribution obtained by simulations. Conclusive illustration recommended a geometrical configuration by which notched samples could display a remarkable plasticity and high strength. It is helpful to material fabrication for metallic glass based porous materials.

scholarly journals Numerical Study on the Fatigue Limit of Metallic Glasses under Cyclic Tension-Compression Loading

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1732
Author(s):  
Jinfeng Yan ◽  
Wenjun Meng ◽  
Zhi Chen ◽  
Hong Guo ◽  
Xianguo Yan
Keyword(s):  
Fatigue Life ◽  
Metallic Glass ◽  
Fatigue Limit ◽  
Free Volume ◽  
Strain Amplitude ◽  
Numerical Study ◽  
Hydrostatic Stress ◽  
Shear Banding ◽  
Engineering Application ◽  
Free Volume Theory

Numerical study was performed to determine the fatigue limit of metallic glass under tension-compression cyclic loading. A revised free-volume theory which considers the hydrostatic stress was utilized to make the predictions. Systematical simulations showed that a higher strain amplitude is prone to making the sample completely damaged earlier. However, lower strain fluctuations could result in a longer fatigue life. Shear banding evolution history described by free-volume localization could reasonably explain the mechanical responses of different samples. In addition, compressive loading could give rise to a higher stress than that under tensile loading because of hydrostatic stress contribution. In the end, a correlation between fatigue life and applied strain amplitude was plotted which could supply a guidance for designing the engineering application of metallic glass under periodic loading.

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 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

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.

Origin of the Simultaneous Improvement of Strength and Plasticity in Ti-based Bulk Metallic Glass Matrix Composites

2005 ◽  
Vol 20 (9) ◽  
pp. 2474-2479 ◽  
Author(s):  
Yu Chan Kim ◽  
Eric Fleury ◽  
Jae-Chul Lee ◽  
Do Hyang Kim
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Coefficient Of Thermal Expansion ◽  
Shear Bands ◽  
Matrix Composites ◽  
The Matrix ◽  
The Difference ◽  
Strength And Plasticity ◽  
Glass Matrix Composites ◽  
Classical Elasticity Theory

W-rich particle-reinforced Ti-based bulk metallic glass (BMG) matrix composites with a compressive strength approaching 3 GPa and a fracture strain of approximately 12% were developed. In contrast to most existing BMG matrix composites, in which the improved ductility was obtained only at the expense of the strength, the composites developed in this study exhibited a significant enhancement in their strength, as well as an improvement in the plasticity. This improvement in the plasticity was attributed to the blocking and circumscription of the shear band propagation, leading to the formation of a large number of shear bands. Using a classical elasticity theory of inclusions, the improvement of the strength was interpreted as resulting from the generation of tensile residual stresses in the matrix due to the difference in the coefficient of thermal expansion between the W-rich particles and the BMG matrix.

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