Liquid-like platinum-rich glasses

Demetriou, Marios D.; Floyd, Michael; Crewdson, Chase; Schramm, Joseph P.; Garrett, Glenn R.; Johnson, William L.

doi:10.1016/j.scriptamat.2011.07.035

Cited by 31 publications

(29 citation statements)

References 10 publications

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“…The predictions suggest that plastic flow in metallic glasses would become completely uniform (implying a suppression of shear banding) when n rises to its limit of 0.5 (the value for a liquid). In isotropic glasses the highest n obtained so far [16] is 0.43, and induced anisotropy may permit even higher values to be reached in particular directions [29]. The present work points towards quite exceptional mechanical properties of metallic glasses as n is increased towards the limit.…”

Section: Discussionmentioning

confidence: 48%

“…(14) and (15) show that, other factors being constant, both l and Du are proportional to ð1À2nÞ=ð1ÀnÞ. Conner et al [5] obtained this result but did not explore it, as their work preceded the current intense interest in how the plasticity of MGs is correlated with their elastic properties (particularly n) [14][15][16][24][25][26]. We now calculate the dependence of l (Fig.…”

Section: Theoretical Analysis Of Shear-band Spacingmentioning

confidence: 81%

“…The link between n and plasticity was noted for metallic glasses by Chen et al [13], and was explored quantitatively by Lewandowski et al [14], who found a sharp transition: Metallic glasses show significant toughness only when n exceeds a critical value of 0.31-0.32. This has excited interest in tuning compositions to increase n, and in this way many tough bulk MGs have been realized [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

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Towards more uniform deformation in metallic glasses: The role of Poisson's ratio

Wei

Lei

Huo

et al. 2013

Materials Science and Engineering: A

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a b s t r a c tWe develop a quantitative analysis of how the plastic deformation in a metallic glass is more uniform if its Poisson ratio n is higher. The plasticity of metallic glasses under ambient conditions is mediated by shear localized in thin bands, and can be characterized by experiments on the bending of thin plates. We extend the analysis by Conner et al. (Conner et al., J. Appl. Phys. 94 (2003), 904-911) of bands in bent plates to include the micromechanics of individual shear bands. Expressions are derived for the shearband spacing and the offset on each band. Both these quantities are predicted to decrease as n is increased. The predictions are tested against measurements on metallic glasses with a wide range of n.Good agreement is found, supporting the new model for the shear-band spacing, and pointing the way towards more diffuse deformation, and consequently improved plasticity and toughness, of metallic glasses as n increases toward the limiting value of 0.5. Crown

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Section: Discussionmentioning

confidence: 48%

Section: Theoretical Analysis Of Shear-band Spacingmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

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Towards more uniform deformation in metallic glasses: The role of Poisson's ratio

Wei

Lei

Huo

et al. 2013

Materials Science and Engineering: A

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“…These colossal changes,which are found even in the sub-percent alloying range as demonstrated by Ref. [4] for 0.5% Ag additions require a different approach compared to the normal alloying of two or more components in the middle of the phase diagram. Changes in the electronic or chemical structure of the global composition are not sufficient to explain the measured large effects by such minor additions.…”

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confidence: 88%

Micro-alloying and the toughness of glasses: Modeling with pinned particles

Dasgupta¹,

Mishra²,

Procaccia³

et al. 2013

Applied Physics Letters

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The usefulness of glasses, and particularly of metallic glasses, in technological applications is often limited by their toughness, which is defined as the area under the stress vs. strain curve before plastic yielding. Recently toughness was found to increase significantly by the addition of small concentrations of foreign atoms that act as pinning centers. We model this phenomenon at zero temperature and quasi-static straining with randomly positioned particles that participate in the elastic deformation but are pinned in the non-affine return to mechanical equilibrium. We find a very strong effect on toughness via the increase of both the shear modulus and the yield stress as a function of the density of pinned particles. Understanding the results calls for analyzing separately the elastic, or "Born term" and the contributions of the "excess modes" that result from glassy disorder. Finally we present a scaling theory that collapses the data on one universal curve as a function of rescaled variables.Introduction: In the field of metallic glasses an old but very important protocol called "micro-alloying" is getting recently very high attention. The protocol comprises the addition of foreign atoms with concentration of the order of 1% to an otherwise regular metallic glass. [4] for 0.5% Ag additions require a different approach compared to the normal alloying of two or more components in the middle of the phase diagram. Changes in the electronic or chemical structure of the global composition are not sufficient to explain the measured large effects by such minor additions. This is also clearly shown in recent toughness measurements [5], where the addition of 1-2% of Si/Sn changes the notch toughness by 50%.In an earlier work [2] it was suggested that the medium range order of the metallic glasses is reorganized and the stress distribution of that reconfiguration [6] causes the change in long range property. In order to verify this suggestion we studied in a most recent MD-simulation [7] the influence of pinned particles on the "global" property of the metallic alloy. Pinning particles in a very small concentration range act like too "big" or too "small" particles that are introduced in a nearly perfect matrix of a glassy system. We found that the β-process of the amorphous system, which is well known to be responsible for aging and diffusion in the glassy state below the glass transition [8] is totally suppressed by a small amount (up to 5%) of pinned particles. This is far below the percolation limit of the system. In this Letter we show that the pinning protocol might provide a general approach to understand the effects of micro-alloying in bulk metallic glasses because it also affects the yield stress, the modulus and the toughness. Predictions are made below for

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“…However, to evaluate this shear localization factor is nontrivial, because that the unstable nature of a mature shear band under unaxial load hinders a thorough investigation on shear banding and that extrinsic factors like the stiffness of the test machine also [19] steps in. Whereas, in bend the propagation of shear bands is largely suppressed by the stress gradient [16,20], leaving an access out of the straits by assuming that the critical strain localization factor is an intrinsic property of MGs (i.e., not depending on the load conditions). Fig.…”

Section: Shear Banding Susceptibilitymentioning

confidence: 99%

An index of shear banding susceptibility of metallic glasses

2016

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a b s t r a c tBy virtue of instability analysis, an index of shear banding susceptibility of metallic glasses (MGs): the critical strain localization factor to initiate an embryonic shear band:c ¼ g b =g m (g b shear strain in the embryonic shear band and g m in the matrix) is derived in analogue to the emergence of geometrically necessary dislocations (GND) in crystals. Physical properties, like Poisson ratioy, Young's modulus E and the surface energy density z, are explicitly incorporated into the formulae of c with which the origin of the plasticity of MGs are unraveled.

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Liquid-like platinum-rich glasses

Cited by 31 publications

References 10 publications

Towards more uniform deformation in metallic glasses: The role of Poisson's ratio

Towards more uniform deformation in metallic glasses: The role of Poisson's ratio

Micro-alloying and the toughness of glasses: Modeling with pinned particles

An index of shear banding susceptibility of metallic glasses

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