A microscopic mechanism for steady state inhomogeneous flow in metallic glasses

Spaepen, Frans

doi:10.1016/0001-6160(77)90232-2

Cited by 2,746 publications

(1,639 citation statements)

References 29 publications

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“…It has been established that an applied stress can cause local atomic rearrangement in metallic glasses, resulting in macroscopic deformation. In particular, a flow equation is usually implemented from transition-state theory, in which the strain-rate scales with the stress as  ε ∝ sinh  Ωσ / 2kT ( ) , where  Ω is the activation volume, k is the Boltzmann constant, and T is the temperature [43][44][45]. Over a particular range of stress, this scaling is quite similar to that of Equation 9, which was found to describe our data well (Table 1).…”

Section: Discussionsupporting

confidence: 73%

Variation of stress with charging rate due to strain-rate sensitivity of silicon electrodes of Li-ion batteries

Pharr

Suo

Vlassak

2014

Journal of Power Sources

103

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Silicon is a promising anode material for lithium-ion batteries due to its enormous theoretical energy density. Fracture during electrochemical cycling has limited the practical viability of silicon electrodes, but recent studies indicate that fracture can be prevented by taking advantage of lithiation-induced plasticity. In this paper, we provide experimental insight into the nature of plasticity in amorphous Li x Si thin films. To do so, we vary the rate of lithiation of amorphous silicon thin films and simultaneously measure stresses. An increase in the rate of lithiation results in a corresponding increase in the flow stress. These observations indicate that rate-sensitive plasticity occurs in a-Li x Si electrodes at room temperature and at charging rates typically used in lithium-ion batteries. Using a simple mechanical model, we extract material parameters from our experiments, finding a good fit to a power law relationship between the plastic strain rate and the stress. These observations provide insight into the unusual ability of a-Li x Si to flow plastically, but fracture in a brittle manner. Moreover, the results have direct ramifications concerning the rate-capabilities of silicon electrodes: faster charging rates (i.e., strain rates) result in larger stresses and hence larger driving forces for fracture.

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Section: Discussionsupporting

confidence: 73%

Variation of stress with charging rate due to strain-rate sensitivity of silicon electrodes of Li-ion batteries

Pharr

Suo

Vlassak

2014

Journal of Power Sources

103

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“…At the microscopic scale, shear-band formation is believed to be associated with the evolution of the local structural order. One atomistic mechanism capturing shear-band formation and evolution in BMGs is the free volume theory developed by Spaepen [17] and further extended by Steif [18]. From a continuum mechanics point of view, the shear-band is a result of strain softening and considered to be a strain-localization phenomenon.…”

Section: Constitutive Relations Of Bmgsmentioning

confidence: 99%

Numerical Modeling of Cyclic Deformation in Bulk Metallic Glasses

Jiang

2016

Metals

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Abstract:In this paper, a systematic numerical simulation was performed to elucidate the damage mechanisms in bulk metallic glasses (BMGs) subjected to the tension-compression cyclic loading, and then the relation between fatigue life, applied strain, and cycling frequency was therefore presented. The free volume was selected as an internal state variable to depict the shear-band nucleation, growth, and coalescence with the help of free volume theory, which was incorporated into the ABAQUS code via a user material subroutine UMAT. Under cyclic loading, the shear banding initiation mainly stems from the microstructure inhomogeneity in BMGs and, further, the effect of applied strain amplitude and cycling frequency was discussed. The present simulations will shed some light on the fatigue damage mechanisms and fatigue life evaluation of BMG structures.

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“…Then Spaepen 73 developed this model by analysis of the mechanism for deformation and dynamics of metal in 1977, which can be used to describe the deformation and fracture of metallic glasses. He thought that there existed some free volumes in amorphous phase and the microscopic plasticity resulted from many single atom-jumps.…”

Section: Free Volume Modelmentioning

confidence: 99%

The Development of Structure Model in Metallic Glasses

et al. 2017

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Metallic glasses (amorphous alloys) have grown from a singular observation to an expansive class of alloys with a broad range of scientific interests. Their unique properties require a robust understanding on the structures at the atomic level while alloys in this class have a similar outlook on the microstructure. In this review, we went through the history of the majority studies on the structure models of metallic glasses, and summarized their historical contributions to the understanding of the structure metallic glasses and the relationship between their structures and properties.

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A microscopic mechanism for steady state inhomogeneous flow in metallic glasses

Cited by 2,746 publications

References 29 publications

Variation of stress with charging rate due to strain-rate sensitivity of silicon electrodes of Li-ion batteries

Variation of stress with charging rate due to strain-rate sensitivity of silicon electrodes of Li-ion batteries

Numerical Modeling of Cyclic Deformation in Bulk Metallic Glasses

The Development of Structure Model in Metallic Glasses

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