THERMODYNAMIC INVESTIGATIONS OF Mg-Cu AND Mg-Ni METALLIC GLASSES

Sommer, F.; Bucher, Gerhard; Predel, B.

doi:10.1051/jphyscol:19808141

Cited by 29 publications

(27 citation statements)

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“…22 This system is interesting because the addition of a small amount of Y makes it a BMG with high strength and low weight. 23 The interatomic potential is the effective medium theory, 24 fitted to properties of the pure elements and intermetallic compounds obtained from experiment and density functional theory calculations.…”

Section: A Potential Obtaining Glassy Configurationsmentioning

confidence: 99%

Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

2006

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We have simulated plastic deformation of a model Mg-Cu metallic glass in order to study shear banding. In uniaxial tension, we find a necking instability occurs rather than shear banding. We can force the latter to occur by deforming in plane strain, forbidding the change of length in one of the transverse directions. Furthermore, in most of the simulations a notch is used to initiate shear bands, which lie at a 45°angle to the tensile loading direction. The shear bands are characterized by the Falk and Langer local measure of plastic deformation D min 2 , averaged here over volumes containing many atoms. The D min 2 profile has a peak whose width is around 10 nm;this width is largely independent of the strain rate. Most of the simulations were, at least nominally, at 100 K, about T g / 3 for this system. The development of the shear bands takes a few tens of ps, once plastic flow has started, more or less independent of strain rate. The shear bands can also be characterized using a correlation function defined in terms of D min 2 , which, moreover, can detect incipient shear bands in cases where they do not fully form. By averaging the kinetic energy over small regions, the local temperature can be calculated, and this is seen to be higher in the shear bands by about 50-100 K. Increases in temperature appear to initiate from interactions of the shear bands with the free surfaces and with each other, and are delayed somewhat with respect to the localization of plastic flow itself. We observe a slight decrease in density, up to 1%, within the shear band, which is consistent with notions of increased free volume or disorder within a plastically deforming amorphous material.

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Section: A Potential Obtaining Glassy Configurationsmentioning

confidence: 99%

Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

2006

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“…Also shown in this figure are experimental observations of glass formation in this binary system, [6] indicating, as previously suggested, [2] that T 0 may be a practical limit for partitionless crystallization.…”

Section: Modeling Resultsmentioning

confidence: 62%

“…The parameters for the liquid phase are evaluated using reported values of activity, [21] chemical potential, [18][19][20][21][22][23] enthalpy of mixing, [17,18] and heat capacity [6] and are listed in Table 4. The heat capacity of the alloy liquid, as modeled with the two-state approach, exhibits a more realistic behavior than our prior treatment, as shown in Fig.…”

Section: Modeling Resultsmentioning

confidence: 99%

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Thermodynamic Treatment of Undercooled Cu-Mg Liquid and the Limits for Partitionless Crystallization

Zhou

Napolitano

2007

J Phs Eqil and Diff

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The thermodynamic properties of the binary Cu-Mg system are examined with a focus on equilibria involving the liquid phase, which is described with a four-species association model, incorporating a two-state treatment for the pure component liquids below their respective melting temperatures. The terminal and intermediate crystalline phases are described as substitutional solid solutions, employing two sublattices for the latter. Model parameters are fitted using available experimental data, and the resulting phase diagram is reported over the full range of compositions in the binary system. We also report the associated T 0 curves, indicating the limits of partitionless crystallization and compare these with reports of amorphous solid formation during rapid solidification processing. The thermodynamic properties of the binary Cu-Mg system are examined with a focus on equilibria involving the liquid phase, which is described with a four-species association model, incorporating a two-state treatment for the pure component liquids below their respective melting temperatures. The terminal and intermediate crystalline phases are described as substitutional solid solutions, employing two sublattices for the latter. Model parameters are fitted using available experimental data, and the resulting phase diagram is reported over the full range of compositions in the binary system. We also report the associated T 0 curves, indicating the limits of partitionless crystallization and compare these with reports of amorphous solid formation during rapid solidification processing.

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“…The simulations in this work mostly use a composition of 15 at.% Cu, which is close to the optimal glass forming composition, although some data are for a larger range of compositions. In the cooling simulations we observe the glass transition around 350 K for this composition, close to the experimental value [15] of 380 K. Measurements of thermodynamic properties and structure are described in detail in Ref. [14].…”

Section: Generating Glassy Configurations and Local Atomic Structurementioning

confidence: 87%

Atomistic simulations of Mg–Cu metallic glasses: mechanical properties

Bailey

Schiøtz

Jacobsen

2004

Materials Science and Engineering: A

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The atomistic mechanisms of plastic deformation in amorphous metals are far from being understood. We have derived potential parameters for molecular dynamics simulations of Mg-Cu amorphous alloys using the Effective Medium Theory. We have simulated the formation of alloys by cooling from the melt, and have used these glassy configurations to carry out simulations of plastic deformation. These involved different compositions, temperatures (including zero), and types of deformation (uniaxial strain/pure shear), and yielded stress-strain curves and values of flow stress. Separate simulations were carried out to study specific features in the stress-strain curves associated with transitions involving internal rearrangements of atoms. Energy barriers were calculated as a function of stress, as was the plastic strain associated with events. The latter leads to a characteristic volume of an event which seems to correspond with the derivative of the barrier with respect to stress.

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THERMODYNAMIC INVESTIGATIONS OF Mg-Cu AND Mg-Ni METALLIC GLASSES

Cited by 29 publications

References 0 publications

Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

Thermodynamic Treatment of Undercooled Cu-Mg Liquid and the Limits for Partitionless Crystallization

Atomistic simulations of Mg–Cu metallic glasses: mechanical properties

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