scholarly journals In Situ Generated Shear Bands in Metallic Glass Investigated by Atomic Force and Analytical Transmission Electron Microscopy

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 111
Author(s):  
Harald Rösner ◽  
Christian Kübel ◽  
Stefan Ostendorp ◽  
Gerhard Wilde
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Local Density ◽  
Shear Bands ◽  
Tensile Tests ◽  
Band Formation ◽  
Atomic Force ◽  
Transmission Electron ◽  
Shear Front

Plastic deformation of metallic glasses performed at temperatures well below the glass transition proceeds via the formation of shear bands. In this contribution, we investigated shear bands originating from in situ tensile tests of Al88Y7Fe5 melt-spun ribbons performed under a transmission electron microscope. The observed contrasts of the shear bands were found to be related to a thickness reduction rather than to density changes. This result should alert the community of the possibility of thickness changes occurring during in situ shear band formation that may affect interpretation of shear band properties such as the local density. The observation of a spearhead-like shear front suggests a propagation front mechanism for shear band initiation here.

Microfracture Observation of Zr-Based Bulk Metallic Glasses

2007 ◽  
Vol 345-346 ◽  
pp. 645-648
Author(s):  
Jung G. Lee ◽  
Kee Sun Sohn ◽  
Sung Hak Lee ◽  
Nack J. Kim ◽  
Choong Nyun Paul Kim
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Fracture Resistance ◽  
Shear Bands ◽  
Stable Crack Growth ◽  
Curve Analysis ◽  
Fracture Properties ◽  
Apparent Fracture Toughness ◽  
Crack Blunting

Microfracture mechanisms of Zr-based bulk metallic glass (BMG) alloy containing ductile crystalline particles were investigated by directly observing microfracture processes using an in situ loading stage. Strength of the BMG alloy containing crystalline particles was lower than that of the monolithic BMG alloy, while ductility was higher. According to the direct microfracture observation, crystalline particles initiated shear bands, acted as blocking sites of shear band or crack propagation, and provided the stable crack growth which could be confirmed by the R-curve analysis, although they negatively affected apparent fracture toughness. This increase in fracture resistance with increasing crack length improved overall fracture properties of the alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching.

scholarly journals Crack Propagation in Metallic Glass Ribbon as a Function of the Position of Stress Concentrators

2017 ◽  
Vol 891 ◽  
pp. 494-499
Author(s):  
Mária Huráková ◽  
Kornel Csach ◽  
Jozef Miškuf ◽  
Alena Juríková ◽  
Václav Ocelík ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Tensile Axis ◽  
Shear Bands ◽  
Glass Ribbon ◽  
Tensile Tests ◽  
In Situ Observation ◽  
Band Formation ◽  
Stress Concentrators ◽  
As Stress

An amorphous metallic ribbon of Fe40Ni40B20 was used for in-situ observation of the crack propagation and shear band formation during tensile tests. Prior to the tensile tests, two holes (with different positions with respect to the tensile axis) were made by laser ablation as stress concentrators. The nucleation and propagation of shear bands on the ribbon surface during tensile tests were analysed with scanning electron microscopy (SEM). At room temperature inhomogeneous plastic deformation of amorphous alloy occurs via the development of primary and secondary shear bands. The influence of the different loading geometry on the topology of shear bands and crack propagation was studied.

scholarly journals Measuring Structural Heterogeneities in Metallic Glasses Using Transmission Electron Microscopy

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1085 ◽  
Author(s):  
Lin Tian ◽  
Cynthia A. Volkert
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Metallic Glasses ◽  
Local Density ◽  
Temporal Correlations ◽  
Transmission Electron ◽  
Excellent Spatial Resolution ◽  
And Performance ◽  
The Stability

Local heterogeneities in the structure and properties of metallic glasses have recently been predicted by computer simulations and also observed in experiments. These heterogeneities are important in understanding the stability and performance of metallic glasses. Progress has been made in measuring heterogeneities in elastic properties and local density down to length scales of less than 10 nm. In this review, we focus on studies of structural and mechanical heterogeneities with emphasis on those achieved by transmission electron microscopy which has an excellent spatial resolution, multifunctional detection modes, as well as in-situ testing capabilities. We argue that the next important step in understanding the behavior of metallic glasses lies in understanding the spatial and temporal correlations between the various structural and mechanical heterogeneities.

Influence of Strain Rate on Shear Localization during Deformation and Fracture of 5754 and 5182 Aluminium Alloy

2006 ◽  
Vol 519-521 ◽  
pp. 1047-1052 ◽  
Author(s):  
Mohammad Jaffar Hadianfard ◽  
Michael J. Worswick
Keyword(s):  
Plastic Deformation ◽  
Shear Band ◽  
Strain Rate ◽  
Shear Bands ◽  
Tensile Tests ◽  
Material Behavior ◽  
Damage Development ◽  
Band Formation ◽  
Deformation And Fracture ◽  
Localized Plastic Deformation

The effect of strain rate in the range of 10-4 to 10-1 s-1 on localization of deformation and fracture behavior of 5754 and 5182 aluminum alloys is investigated. For this study, tensile tests, interrupted tensile tests, shear band decoration, fractography and image analysis has been used. This investigation is based on experimental work and observation of the material behavior. Results show that strain rate has some effect on the mechanical properties and deformation stability of the alloys. The area of localized plastic deformation and thickness of the shear bands were found to be sensitive to the strain rate. It was also observed that localization of plastic deformation and shear band formation is an important step in the damage propagation and final fracture of the alloys. Detail of damage development, based upon micrographs of samples interrupted at different stages of straining is presented

scholarly journals Molecular Dynamics Simulation of Structural Signals of Shear-Band Formation in Zr46Cu46Al8 Metallic Glasses

Materials ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 2564
Author(s):  
Shi-Dong Feng ◽  
Keith Chan ◽  
Lei Zhao ◽  
Li-Min Wang ◽  
Ri-Ping Liu
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Shear Band ◽  
Metallic Glasses ◽  
Orientational Order ◽  
Shear Bands ◽  
Dynamics Simulation ◽  
Shear Band Formation ◽  
Band Formation ◽  
Average Size

The evolution from initiation to formation of a shear band in Zr46Cu46Al8 metallic glasses is presented via molecular dynamics simulation. The increase in number and the decrease in average size of clusters with the quasi-nearest atoms being 0 correspond to the shear-band evolution from initiation to formation. When the shear band is completely formed, the distribution of the bond orientational order q6 reaches a minimum. The maximum of the number of the polyhedral loss of Cu-centered <0, 0, 12, 0> and the minimum of the number of the polyhedral loss of Zr-centered <0, 2, 8, 5> correspond to the shear-band formation. These findings provide a strong foundation for characterizing the evolution from initiation to formation of shear bands.

scholarly journals An Insight into Amorphous Shear Band in Magnetorheological Solid by Atomic Force Microscope

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4384
Author(s):  
Mohd Aidy Faizal Johari ◽  
Asmawan Mohd Sarman ◽  
Saiful Amri Mazlan ◽  
Ubaidillah U ◽  
Nur Azmah Nordin ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Shear Band ◽  
Shear Bands ◽  
Test Duration ◽  
Phase Imaging ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Matrix ◽  
Relaxation Stress ◽  
Band Deformation

Micro mechanism consideration is critical for gaining a thorough understanding of amorphous shear band behavior in magnetorheological (MR) solids, particularly those with viscoelastic matrices. Heretofore, the characteristics of shear bands in terms of formation, physical evolution, and response to stress distribution at the localized region have gone largely unnoticed and unexplored. Notwithstanding these limitations, atomic force microscopy (AFM) has been used to explore the nature of shear band deformation in MR materials during stress relaxation. Stress relaxation at a constant low strain of 0.01% and an oscillatory shear of defined test duration played a major role in the creation of the shear band. In this analysis, the localized area of the study defined shear bands as varying in size and dominantly deformed in the matrix with no evidence of inhibition by embedded carbonyl iron particles (CIPs). The association between the shear band and the adjacent zone was further studied using in-phase imaging of AFM tapping mode and demonstrated the presence of localized affected zone around the shear band. Taken together, the results provide important insights into the proposed shear band deformation zone (SBDZ). This study sheds a contemporary light on the contentious issue of amorphous shear band deformation behavior and makes several contributions to the current literature.

scholarly journals Fracture in Bulk Amorphous Alloys

1998 ◽  
Vol 554 ◽  
Author(s):  
J. A. Horton ◽  
J. L. Wright ◽  
J. H. Schneibel
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Shear Bands ◽  
Bulk Amorphous Alloy ◽  
In Situ Tem ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Crack Tips ◽  
Temperature Fracture

AbstractThe fracture behavior of a Zr-based bulk amorphous alloy, Zr-10 Al-5 Ti-17.9 Cu-14.6Ni (at.%), was examined by transmission electron microscopy (TEM) and x-ray diffraction forany evidence of crystallization preceding crack propagation. No evidence for crystallizationwas found in shear bands in compression specimens or at the fracture surface in tensile specimens.In- situ TEM deformation experiments were performed to more closely examine actualcrack tip regions. During the in-situ deformation experiment, controlled crack growth occurredto the point where the specimen was approximately 20 μm thick at which point uncontrolledcrack growth occurred. No evidence of any crystallization was found at the crack tips or thecrack flanks. Subsequent scanning microscope examination showed that the uncontrolledcrack growth region exhibited ridges and veins that appeared to have resulted from melting. Performing the deformations, both bulk and in-situ TEM, at liquid nitrogen temperatures (LN2) resulted in an increase in the amount of controlled crack growth. The surface roughness of the bulk regions fractured at LN2 temperatures corresponded with the roughness of the crack propagation observed during the in-situ TEM experiment, suggesting that the smooth-appearing room temperature fracture surfaces may also be a result of localized melting.

Dynamic Failure Mechanisms in Beryllium-Bearing Bulk Metallic Glasses

1998 ◽  
Vol 554 ◽  
Author(s):  
David M. Owen ◽  
Ares J. Rosakis ◽  
William L. Johnson
Keyword(s):  
Crack Initiation ◽  
Shear Band ◽  
Metallic Glasses ◽  
Impact Loading ◽  
High Speed ◽  
Failure Mechanisms ◽  
Shear Bands ◽  
Dynamic Crack ◽  
Dynamic Failure ◽  
Asymmetric Impact

AbstractThe understanding of dynamic failure mechanisms in bulk metallic glasses is important for the application of this class of materials to a variety of engineering problems. This is true not only for design environments in which components are subject to high loading rates, but also when components are subjected to quasi-static loading conditions where observations have been made of damage propagation occurring in an unstable, highly dynamic manner. This paper presents preliminary results of a study of the phenomena of dynamic crack initiation and growth as well as the phenomenon of dynamic localization (shear band formation) in a beryllium-bearing bulk metallic glass, Zr41.25Ti13.75Ni10Cu12.75Be22.5. Pre-notched and prefatigued plate specimens were subjected to quasi-static and dynamic three-point bend loading to investigate crack initiation and propagation. Asymmetric impact loading with a gas gun was used to induce dynamic shear band growth. The mechanical fields in the vicinity of the dynamically loaded crack or notch tip were characterized using high-speed optical diagnostic techniques. The results demonstrated a dramatic increase in the crack initiation toughness with loading rate and subsequent crack tip speeds approaching 1000 m s−1. Dynamic crack tip branching was also observed under certain conditions. Shear bands formed readily under asymmetric impact loading. The shear bands traveled at speeds of approximately 1300 m s−1 and were accompanied by intense localized heating measured using high-speed full-field infrared imaging. The maximum temperatures recorded across the shear bands were in excess of 1500 K.

Rate dependence of serrated flow in a metallic glass

2003 ◽  
Vol 18 (4) ◽  
pp. 755-757 ◽  
Author(s):  
W. H. Jiang ◽  
M. Atzmon
Keyword(s):  
Plastic Deformation ◽  
Atomic Force Microscopy ◽  
Loading Rate ◽  
Shear Bands ◽  
Shear Band Formation ◽  
Band Formation ◽  
Serrated Flow ◽  
Force Microscopy ◽  
Loading Rates ◽  
Atomic Force

Plastic deformation of amorphous Al90Fe5Gd5 was investigated using nanoindentation and atomic force microscopy. While serrated flow was detected only at high loading rates, shear bands were observed for all loading rates, ranging from 1 to 100 nm/s. However, the details of shear-band formation depend on the loading rate.

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