Impurity Diffusion in Zr-Ti-Cu-Ni-Be Bulk Glasses

Budke, E.; Fielitz, P.; Macht, M.‐P.; Naundorf, V.; Frohberg, G.

doi:10.4028/www.scientific.net/ddf.143-147.825

Cited by 28 publications

(9 citation statements)

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“…This value is close to the value attributed to titanium diffusion in Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5 (4.09 ± 0.76 eV) [37,38]. Our E c values are close to these values and suggest that bulk crystallization in Cu 47 Ti 33 Zr 11 Ni 8 Si 1 gas atomized powders in the supercooled liquid may also be dominated by Ti diffusion.…”

Section: Discussionsupporting

confidence: 83%

Nanocrystal development in Cu47Ti33Zr11Ni8Si1 metallic glass powders

Venkataraman

Löser

Eckert

et al. 2006

Journal of Alloys and Compounds

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Section: Discussionsupporting

confidence: 83%

Nanocrystal development in Cu47Ti33Zr11Ni8Si1 metallic glass powders

Venkataraman

Löser

Eckert

et al. 2006

Journal of Alloys and Compounds

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“…Since Be is the smallest component in both glasses, Be motions should dominate the observed slow motions. Comparison of measured diffusion constants of Be and other elements in vit1 and vit4 also supports this assumption [6]. The measured V is thus attributed to the Be jump frequency.…”

Section: Vsupporting

confidence: 55%

“…[S0031-9007 (98) The nature of atomic transport in metallic glasses has been the subject of numerous studies over the past decade and still remains a controversial and highly debated issue. Traditional techniques employed for diffusion study in metallic glasses include radioactive tracer [1,2], secondary ion mass spectrometry [3][4][5][6], and elastic backscattering (EBS) [7]. These techniques are based on the analysis of long-range diffusion and do not probe directly the characteristics of short-range atomic motions.…”

mentioning

confidence: 99%

Slow Atomic Motion in Zr-Ti-Cu-Ni-Be Metallic Glasses Studied by NMR

et al. 1998

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Nuclear magnetic resonance is used for the first time to detect slow atomic motion in metallic glasses, specifically, Be motion in Zr-Ti-Cu-Ni-Be bulk metallic glasses. The observations are not consistent with the vacancy-assisted and interstitial diffusion mechanisms and favor the spread-out free volume fluctuation mechanism for Be diffusion. Comparison with the results of Be diffusion measured by elastic backscattering the NMR results also indicates that the energy barriers for short-and long-range Be motion are the same. [S0031-9007 (98) The nature of atomic transport in metallic glasses has been the subject of numerous studies over the past decade and still remains a controversial and highly debated issue. Traditional techniques employed for diffusion study in metallic glasses include radioactive tracer [1,2], secondary ion mass spectrometry [3][4][5][6], and elastic backscattering (EBS) [7]. These techniques are based on the analysis of long-range diffusion and do not probe directly the characteristics of short-range atomic motions. For instance, possible spatial inhomogeneity of atomic motions cannot be probed directly by these techniques [1]. In contrast, nuclear magnetic resonance (NMR) is a direct probe of local atomic motions and has made significant contributions to the understanding of motions in polymeric and oxide glassy systems [8][9][10][11][12] and in crystalline metals and alloys [13][14][15][16]. So far, the potential of NMR has not been realized in studying atomic motions in metallic glasses [12].Recently, bulk metallic glasses Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 -Be 22.5 (vit1) and Zr 46.75 Ti 8.25 Cu 7.5 Ni 10 Be 27.5 (vit4) with extraordinarily high glass forming ability and thermal stability were discovered [17,18]. The Be diffusivity in both glasses was found by EBS to follow Arrhenius behavior below T g ͑ഠ625 K͒ with activation enthalpy of 1

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“…The sample referring to the highest annealing temperature of 713 K was partially crystallized and was not taken into account, although the very small isotope effect (Table I) indicates that effects from diffusion in the crystalline phase, where much larger isotope effects are expected [28], are negligible. Results for Be and Al diffusion in the amorphous alloy are shown for comparison [29,30]. Only the Al data originate from direct tracer measurements by means of secondary ion mass spectrometry.…”

Section: Mass Dependence Of Diffusion In a Supercooled Metallic Meltmentioning

confidence: 99%

Mass Dependence of Diffusion in a Supercooled Metallic Melt

et al. 1998

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The isotope effect E °D a ͞D b 2 1 ¢ ͑͞ p m b ͞m a 2 1͒ of cobalt diffusion in the deeply supercooled melt of the metallic alloy Zr 46.7 Ti 8.3 Cu 7.5 Ni 10 Be 27.5 has been measured employing the radiotracers 57 Co and 60 Co. The isotope effect is very small, E 0.09 6 0.03, and exhibits no significant temperature dependence in a range up to 120 K above the calorimetric glass transition temperature T g , encompassing almost 3 orders of magnitude in the diffusivity. This result suggests that long-range diffusion in the deeply supercooled melt is not mediated by viscous flow but rather proceeds by collective hopping processes involving about ten atoms. [S0031-9007(98)06275-9] PACS numbers: 66.10. Cb, 66.30.Fq, 64.70.Dv Atomic transport in liquids and glasses has been the subject of many theoretical and experimental investigations, particularly in connection with the glass transition [1,2]. Diffusion in ordinary liquids at high temperatures is well understood. In this hydrodynamic regime all atoms contribute continuously to the mean square atomic displacement, and diffusion takes place via viscous flow, as described by the Stokes-Einstein relation [3]. Microscopically, transport in the hydrodynamic regime is governed by uncorrelated binary collisions of atoms. Kinetic theories for a simple liquid [3,4] predict the following mass and temperature dependence of the diffusivity D:where m is the atomic mass and n is close to 2 according to molecular dynamics simulations [1] and experiments [5]. Upon supercooling a liquid or melt the viscosity increases markedly because, due to the increase in density, atoms are more and more trapped in their nearest-neighbor "cages" for times much longer than the vibration time.According to the mode coupling theory [6] this cage effect causes viscous flow to freeze in at a critical temperature T c . Below T c , which is typically some 20% above the caloric glass transition temperature T g [7], long-range diffusion in the supercooled liquid is expected to occur only via thermally activated hopping processes. Molecular dynamics simulations have shown the transition from viscous flow at high temperatures to hopping in the glassy state [8][9][10]. The coexistence of both processes was observed in a certain temperature range in the supercooled liquid state. Moreover, computer simulations as well as neutron scattering [11] have confirmed the existence of a critical temperature above T g , where the decay of density correlations slows down drastically. Whereas generally hopping in crystalline solids is a single-atom jump process [12], recent extensions of the mode coupling theory to the glassy state envision hop-ping in glasses as a highly cooperative medium-assisted process [13]. Highly collective hopping processes have indeed been observed in molecular dynamics simulations [10,14,15]. These simulations reveal chainlike displacements involving some ten atoms, which are suggested to be closely related to the well known low frequency excitations in glasses [14]. While, depending on the alloy ...

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Impurity Diffusion in Zr-Ti-Cu-Ni-Be Bulk Glasses

Cited by 28 publications

References 0 publications

Nanocrystal development in Cu47Ti33Zr11Ni8Si1 metallic glass powders

Nanocrystal development in Cu47Ti33Zr11Ni8Si1 metallic glass powders

Slow Atomic Motion in Zr-Ti-Cu-Ni-Be Metallic Glasses Studied by NMR

Mass Dependence of Diffusion in a Supercooled Metallic Melt

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