Evolution of shear bands into cracks in metallic glasses

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.

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Shear bands in metallic glasses

Materials Science and Engineering R Reports ◽

10.1016/j.mser.2013.04.001 ◽

2013 ◽

Vol 74 (4) ◽

pp. 71-132 ◽

Cited By ~ 827

Author(s):

A.L. Greer ◽

Y.Q. Cheng ◽

E. Ma

Keyword(s):

Metallic Glasses ◽

Shear Bands

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The Significant Impact of Carbon Nanotubes on the Electrochemical Reactivity of Mg-Bearing Metallic Glasses with High Compressive Strength

Materials ◽

10.3390/ma12182989 ◽

2019 ◽

Vol 12 (18) ◽

pp. 2989 ◽

Cited By ~ 1

Author(s):

Lou ◽

Cheng ◽

Zhao ◽

Misra ◽

Feng

Keyword(s):

Carbon Nanotubes ◽

Compressive Strength ◽

Corrosion Resistance ◽

Metallic Glasses ◽

Fracture Strain ◽

Amorphous Material ◽

Shear Bands ◽

The Matrix ◽

Superior Mechanical Properties ◽

Pressure Die Casting

Here, we elucidate the significant impact of carbon nanotubes (CNTs) on the electrochemical behavior of Mg-based amorphous composite materials that were reinforced with CNTs while using pressure die casting. The addition of 3 vol % CNTs led to an increase in the compressive strength of Mg-based amorphous material from 812 MPa to 1007 MPa, and the fracture strain from 1.91% to 2.67% in the composite. Interestingly, the addition of CNTs significantly contributed to the enhancement of corrosion resistance of Mg-based glass by ~30%. The superior mechanical properties are primarily related to the fact that the addition of CNTs hindered the growth of shear bands (cracks), while the high corrosion resistance is related to inferior wettability and the bridging effect between adherent corrosive oxide film and the matrix that provided enhanced corrosion resistance.

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Specific Features of Structure Transformation and Properties of Amorphous-Nanocrystalline Alloys

Metals ◽

10.3390/met10030358 ◽

2020 ◽

Vol 10 (3) ◽

pp. 358 ◽

Cited By ~ 1

Author(s):

Alexandr Aronin ◽

Galina Abrosimova

Keyword(s):

Amorphous Phase ◽

Metallic Glasses ◽

Amorphous Alloys ◽

Structural Changes ◽

Shear Bands ◽

Component Composition ◽

Amorphous Structure ◽

Structure Evolution ◽

Current State ◽

Heterogeneous Phase

This work is devoted to a brief overview of the structure and properties of amorphous-nanocrystalline metallic alloys. It presents the current state of studies of the structure evolution of amorphous alloys and the formation of nanoglasses and nanocrystals in metallic glasses. Structural changes occurring during heating and deformation are considered. The transformation of a homogeneous amorphous phase into a heterogeneous phase, the dependence of the scale of inhomogeneities on the component composition, and the conditions of external influences are considered. The crystallization processes of the amorphous phase, such as the homogeneous and heterogeneous nucleation of crystals, are considered. Particular attention is paid to a volume mismatch compensation on the crystallization processes. The effect of changes in the amorphous structure on the forming crystalline structure is shown. The mechanical properties in the structure in and around shear bands are discussed. The possibility of controlling the structure of fully or partially crystallized samples is analyzed for creating new materials with the required physical properties.

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