Characterization of Free Volume in a Bulk Metallic Glass Using Positron Annihilation Spectroscopy

Flores, Katharine M.; Suh, Daewoong; Dauskardt, R.H.; Asoka‐Kumar, P.; Sterne, P. A.; Howell, R.H.

doi:10.1557/jmr.2002.0171

Cited by 150 publications

(103 citation statements)

References 17 publications

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“…It is known that most of the bulk metallic glasses show strong liquid behavior and generally have a fragility index of less than 50 [19,22,23]. And a reduced m=42/β relation can be derived from a relation between the fragility index m and stretching exponent β based on the defect diffusion model proposed by Bendler et al [24], this expression has been confirmed to be suitable for describing the m-β relation for polymeric, alcoholic and metallic glasses.…”

Section: Discussionmentioning

confidence: 77%

Structural relaxation of Ti40Zr25Ni8Cu9Be18 bulk metallic glass

Mei

Soubeyroux

Blandin

et al. 2011

Journal of Non-Crystalline Solids

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The enthalpy relaxation behavior of Ti 40 Zr 25 Ni 8 Cu 9 Be 18 bulk metallic glass follows the general characteristics of that for amorphous materials although its unique quenched-in nuclei/amorphous matrix structure: the annealing time dependence of recovery enthalpy follows a stretched exponential function with the mean relaxation time obeying an Arrhenius law, which may be due to the longer incubation time for crystallization τ inc than the relaxation time τ leading to the enthalpy relaxation Two parameters, β g and τ g , representing the stretching exponent and the mean structural relaxation time at the calorimetric glass transition temperature, respectively, are correlated with glass forming ability and thermal stability, respectively. The high value of β g for Ti 40 Zr 25 Ni 8 Cu 9 Be 18 BMG that is much higher than 0.84 and approaches unity reveals its good glass forming ability; however, its low value of τ g indicates a worse thermal stability compared with typical BMGs.

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Section: Discussionmentioning

confidence: 77%

Structural relaxation of Ti40Zr25Ni8Cu9Be18 bulk metallic glass

Mei

Soubeyroux

Blandin

et al. 2011

Journal of Non-Crystalline Solids

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“…Free volume change induced by plastic deformation has been investigated by using various techniques such as positron annihilation, 9,10) direct density measurement, 11,12) TEM and SEM observation, 2,3) fluctuation electron microscopy, 13) and so on. However, the experimental techniques have inherent limitations in spatial and temporal resolutions; and most tests have to be performed after sample failure.…”

Section: Introductionmentioning

confidence: 99%

Free Volume Evolution in Metallic Glasses Subjected to Mechanical Deformation

2007

Mater. Trans.

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We define the Turnbull-Cohen free volume as the critical excess of the Voronoi volume of an atom less its core volume. Using molecular dynamics simulation we calculated the free volume change in two model binary metallic glasses undergoing tension and shear deformation. We show that the free volume change is an integral part of the deformation process; and the shear localization manifested as a shear band is directly related to the inhomogeneous distribution of the free volumes. Shear band formation may consist of two stages: the initial free volume production in the amorphous solids and the liquefaction of the regions with accumulated deformation strains. We show, for the first time, the formation of voids and the ''vein'' patterns on fracture surfaces at atomic scales; they are the combined result of the free volume change and loading and sample conditions.

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“…A similar restriction is imposed on the positron lifetime s, which is sensitive to differences in electron density and is prolonged in vacancies. [12][13][14][15] Room temperature density q (Refs. 8,[15][16][17] is a convenient, but not real-time, parameter.…”

Section: Introductionmentioning

confidence: 99%

Characteristic free volume change of bulk metallic glasses

Zeng

2012

Journal of Applied Physics

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Transport properties of silver selenomolybdate glassy ionic conductors J. Appl. Phys. 112, 094110 (2012) Shock-induced intermediate-range structural change of SiO2 glass in the nonlinear elastic region Appl. Phys. Lett. 101, 181901 (2012) Rattler model of the boson peak at silica surfaces J. Chem. Phys. 137, 164702 (2012) Void structure in silica glass with different fictive temperatures observed with positron annihilation lifetime spectroscopy Appl. Phys. Lett. 101, 164103 (2012) Local structure origin of higher glass forming ability in Ta doped Co65B35 amorphous alloy J. Appl. Phys. 112, 073520 (2012) Additional information on J. Appl. Phys. The free volume change DV f ðTÞ of bulk metallic glasses (BMGs) relative to a hypothesized amorphous reference state was measured using the thermal dilatation method. The characteristic free volume change, i.e., the free volume released in structural relaxation DV f-sr , was identified quantitatively from the DV f ðTÞ curve. For a Fe-based BMG, it was found that DV f-sr increases with decreases in the sample diameter and heating rate. DV f-sr measured under the same sample diameter and heating rate conditions allowed the convenient comparison of different BMGs. The comparison revealed that the glass-forming ability (GFA) enhancement of each of two Pd-, Mg-, Cu-, Zr-, Ti-, and Fe-based BMGs can be sensitively reflected in the decrease in DV f-sr and the narrowing of the difference between the peak temperature of the thermal expansion coefficient and the end temperature of the glass transition process. In addition, for these twelve typical BMGs, there is a good linear relationship between DV f-sr and LogD 2 c or LogD c , where D c is the critical diameter. DV f-sr is thus sensitive to and has a close correlation with GFA. Furthermore, the DV f-sr measurement results are in good agreement with the free volume change measured with the specific heat capacity, room temperature density, and positron annihilation lifetime methods. In the study of the relationship between the structure and properties of BMGs, DV f-sr thus plays an important role given its comparability and convenience. V C 2012 American Institute of Physics.

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Characterization of Free Volume in a Bulk Metallic Glass Using Positron Annihilation Spectroscopy

Cited by 150 publications

References 17 publications

Structural relaxation of Ti40Zr25Ni8Cu9Be18 bulk metallic glass

Structural relaxation of Ti40Zr25Ni8Cu9Be18 bulk metallic glass

Free Volume Evolution in Metallic Glasses Subjected to Mechanical Deformation

Characteristic free volume change of bulk metallic glasses

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