Mechanical glass transition revealed by the fracture toughness of metallic glasses

Ketkaew, Jittisa; Chen, Wen; Wang, Hui; Datye, Amit; Meng, Fan; Pereira, Gabriela Ribeiro; Schwarz, Udo D.; Liu, Ze; Yamada, R.; Dmowski, W.; Shattuck, Mark D.; O’Hern, Corey S.; Egami, T.; Bouchbinder, Eran; Schroers, Jan

doi:10.1038/s41467-018-05682-8

Cited by 125 publications

(70 citation statements)

References 43 publications

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“…Moreover, improved control over structural disorder in glasses, e.g. as recently done in [46], can affect the crossover to Rayleigh scaling and make it accessible to present-day measurement techniques.…”

Section: Experimental Evidencementioning

confidence: 99%

Wave attenuation in glasses: Rayleigh and generalized-Rayleigh scattering scaling

Moriel

Kapteijns

Rainone

et al. 2019

The Journal of Chemical Physics

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The attenuation of long-wavelength phonons (waves) by glassy disorder plays a central role in various glass anomalies, yet it is neither fully characterized, nor fully understood. Of particular importance is the scaling of the attenuation rate Γ(k) with small wavenumbers k → 0 in the thermodynamic limit of macroscopic glasses. Here we use a combination of theory and extensive computer simulations to show that the macroscopic low-frequency behavior emerges at intermediate frequencies in finite-size glasses, above a recently identified crossover wavenumber k † , where phonons are no longer quantized into bands. For k < k † , finite-size effects dominate Γ(k), which is quantitatively described by a theory of disordered phonon bands. For k > k † , we find that Γ(k) is affected by the number of quasilocalized nonphononic excitations, a generic signature of glasses that feature a universal density of states. In particular, we show that in a frequency range in which this number is small, Γ(k) follows a Rayleigh scattering scaling ∼ kd +1 (d is the spatial dimension), and that in a frequency range in which this number is sufficiently large, the recently observed generalized-Rayleigh scaling of the form ∼ kd +1 log(k0/k) emerges (k0 > k † is a characteristic wavenumber). Our results suggest that macroscopic glasses -and, in particular, glasses generated by conventional laboratory quenches that are known to strongly suppress quasilocalized nonphononic excitations -exhibit Rayleigh scaling at the lowest wavenumbers k and a crossover to generalized-Rayleigh scaling at higher k. Some supporting experimental evidence from recent literature is presented.

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Section: Experimental Evidencementioning

confidence: 99%

Wave attenuation in glasses: Rayleigh and generalized-Rayleigh scattering scaling

Moriel

Kapteijns

Rainone

et al. 2019

The Journal of Chemical Physics

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“…We are instead interested in rejuvenation to states of higher energy (and correspondingly higher fictive temperature, Tfict), which are obtainable by faster cooling, irradiation or thermomechanical processing 5 . Such states can, for example, show an abrupt toughening transition as Tfict is increased 12 . A rejuvenated MG with reduced σy might show hardening, instead of softening, as flow progresses, and in this regime there would be no localization of shear ( Fig.…”

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confidence: 99%

Strain-hardening and suppression of shear-banding in rejuvenated bulk metallic glass

Pan

Ivanov

Zhou

et al. 2020

Nature

261

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Strain-hardening (the increase of flow stress with plastic strain) is the most important phenomenon in the mechanical behaviour of engineering alloys because it ensures that flow is delocalized, enhances tensile ductility and inhibits catastrophic mechanical failure 1,2. Metallic glasses (MGs) lack the crystallinity of conventional engineering alloys, and some of their properties-such as higher yield stress and elastic strain limit 3-are greatly improved relative to their crystalline counterparts. MGs can have high fracture toughness and have the highest known 'damage tolerance' (defined as the product of yield stress and fracture toughness) 4 among all structural materials. However, the promise of MGs for structural applications is largely thwarted by the fact that they show strain-softening, instead of strain-hardening; this leads to extreme localization of plastic flow in shear bands, and is associated with early catastrophic failure in tension. Although rejuvenation of an MG (raising its energy to values that are typical of glass formation at a higher cooling rate) lowers its yield stress, which might enable strain-hardening 5 , it is unclear whether sufficient rejuvenation can be achieved in bulk samples while retaining their glassy structure. Here we show that plastic deformation under triaxial compression at room temperature can rejuvenate bulk MG samples sufficiently to enable strain-hardening through a mechanism that has not been previously observed in the metallic state. This transformed behaviour suppresses shear-banding in bulk samples in normal uniaxial (tensile or compressive) tests,

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“…The fictive temperature T f is defined as the glass transition upon cooling and therefore depends on the applied cooling rate 17 . T f of a glass can also be changed by annealing or rejuvenation 18,19 . However, T f critical is an inherent property of the alloy composition and should be connected to the structure of the glass.…”

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confidence: 99%

Signatures of structural differences in Pt–P- and Pd–P-based bulk glass-forming liquids

et al. 2019

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The structural differences between the compositionally related Pt-P-and Pd-P-based bulk glass-forming liquids are investigated in synchrotron X-ray scattering experiments. Although Pt and Pd are considered to be topologically equivalent in structural models, we show that drastic changes in the total structure factor and in the reduced pair distribution function are observed upon gradual substitution. These variations indicate the existence of significant structural differences on the short-(SRO) and medium-range order (MRO) length scale. The structural data suggest that the distribution of the dominant polyhedra and the distribution of their connection schemes gradually change from Pt-P-to Pd-P-based alloys, which is likely connected to the different sensitivities to annealing or cooling rate induced embrittlement. The evolution of the total structure factor and the reduced pair distribution function with increasing temperature indicate the (partial) dissolution of both, the MRO and the SRO, which reflects the thermodynamic properties of the liquids.

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Mechanical glass transition revealed by the fracture toughness of metallic glasses

Cited by 125 publications

References 43 publications

Wave attenuation in glasses: Rayleigh and generalized-Rayleigh scattering scaling

Wave attenuation in glasses: Rayleigh and generalized-Rayleigh scattering scaling

Strain-hardening and suppression of shear-banding in rejuvenated bulk metallic glass

Signatures of structural differences in Pt–P- and Pd–P-based bulk glass-forming liquids

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