Analysis of nanocrystal development in Al-Y-Fe and Al-Sm glasses

Foley, Jim; Allen, Douglas; Perepezko, John H.

doi:10.1016/1359-6462(96)00196-0

Cited by 139 publications

(65 citation statements)

References 11 publications

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“…Separate analysis based on crystallization kinetics and nucleation densities indicates critical cluster sizes in the range of 8 -15 Å ͑Ref. 18͒ which is close to previous estimates 19 and represents a satisfactory consistency. More accurate measurements of the cluster size distribution require systematic variable resolution FEM.…”

supporting

confidence: 62%

“…Devitrification of rapidly quenched amorphous Al 92 Sm 8 at Ͻ250°C produces pure Al nanocrystals at concentrations Ͼ10 21 m −3 . 2,3 Devitrification of Al 92 Sm 8 amorphized by deformation does not proceed by primary Al crystallization. 3 When annealed below T g , the melt-spun material exhibits a steadily decreasing nucleation rate, 4 which suggests heterogeneous nucleation.…”

mentioning

confidence: 99%

“…2,3,15 At a given annealing temperature, some of those clusters are supercritical and grow into stable crystals, which predicts the observed decrease in nucleation rate under isothermal annealing. 4 Figure 2 shows that the degree of MRO, indicated by the height of the peaks, 16 is reduced by the same isothermal anneal.…”

mentioning

confidence: 99%

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Aluminum nanoscale order in amorphous Al92Sm8 measured by fluctuation electron microscopy

Stratton

Hamann

Perepezko

et al. 2005

Applied Physics Letters

103

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When annealed below T g , the melt-spun material exhibits a steadily decreasing nucleation rate, 4 which suggests heterogeneous nucleation. 5 The nucleation site has so far eluded structural or chemical detection, ruling out common sites like second phase interfaces or large impurity clusters. This suggests that the nucleation sites in quenched Al 92 Sm 8 may be a form of nanometer-length structure or medium-range order ͑MRO͒. Such structure is difficult to detect in amorphous materials using conventional techniques such as x-ray diffraction. 6 Here, we report fluctuation electron microscopy ͑FEM͒ ͑Refs. 7 and 8͒ measurements and simulations which find MRO associated with primary crystallization in amorphous Al 92 Sm 8 .FEM measures diffraction from nanoscale volumes using dark-field transmission electron microscopy ͑TEM͒ at a deliberately low ͑5-50 Å͒ image resolution. The magnitude of the spatial fluctuations in diffraction, measured by the normalized variance V as a function of scattering vector k, gives information about MRO at the length scale of the image resolution. 7,9 V͑k͒ depends on the three-and four-body atomic position correlation functions. 9 Peaks in V͑k͒ give information about the type of MRO from their position in k and the degree of MRO from their height. A polycrystalline sample is an extreme example of order: in a dark-field image each grain will appear brightest when it satisfies a Bragg condition in k, leading to a high peaks in V͑k͒ at the crystal reciprocal lattice k's.Samples of amorphous Al 92 Sm 8 were prepared by rapid quenching in a single wheel melt spinner at a tangential wheel speed of 55 m / s and by cold-rolling elemental foil multilayers at a 0.003 s −1 strain rate. Melt-spun ribbon samples were annealed at 130°C ͑ϽT g of 171°C͒ 3,10 under vacuum. TEM samples were prepared by electropolishing only, as ion milling can introduce spurious peaks in V͑k͒ of amorphous metals. 11 FEM was done in hollow-cone darkfield mode on a LEO 912 EFTEM at 120 kV and 16 Å resolution. Each V͑k͒ data set is the mean of measurements from at least seven areas of the sample, quoted with one standard deviation of the mean error bars.

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confidence: 62%

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confidence: 99%

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Aluminum nanoscale order in amorphous Al92Sm8 measured by fluctuation electron microscopy

Stratton

Hamann

Perepezko

et al. 2005

Applied Physics Letters

103

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“…It is well known that crystallization of amorphous Al-TM-RE alloys usually proceeds in several stages [8][9][10] but their clear interpretation is often complicated. Moreover, the mechanism of nanocrystal phase formation for these alloys is still the matter of debates [11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Crystallization kinetics of Al86Ni8Gd6 amorphous alloy

Kulikova

Быков

Belozerova

et al. 2013

Journal of Non-Crystalline Solids

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We study structure and crystallization kinetics of melt-spun Al 86 Ni 8 Gd 6 amorphous alloy. The X-ray diffraction and transmission electron microscopy detect pronounced nanoscale clusters in the structure of the amorphous state. Differential scanning calorimetry analysis shows complex three-stage crystallization of the amorphous alloy at different heating rates. The high temperature X-ray diffraction analysis reveals crystallization mechanism with competing reactions of intermetallic compounds formation. Summarizing the experimental data, we introduce multiversion non-linear kinetic model that describes the crystallization process completely and allows us to determine kinetic parameters with high accuracy. The activation energies obtained reveal relatively stable amorphous state.

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“…% Al) [8][9][10]. To understand the origin of crystallization, various competing models have been proposed, such as heterogeneous nucleation [11], the presence of a large density of quenched-in nuclei in the amorphous [2,12], a new kind of homogeneous nucleation mechanism ('linked flux') [13,14] and a phase separation mechanism which indicates nucleation of fcc-Al arises at the interface of the phase separation regions [15]. However, the correct crystallization mechanism has yet to be identified in the Albased metallic glasses.…”

Section: Introductionmentioning

confidence: 99%

Relation Between Medium-Range Order and Crystallization in Al-Ni Based Metallic Glass

Wang¹

2011

TOMSJ

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Analysis of nanocrystal development in Al-Y-Fe and Al-Sm glasses

Cited by 139 publications

References 11 publications

Aluminum nanoscale order in amorphous Al92Sm8 measured by fluctuation electron microscopy

Aluminum nanoscale order in amorphous Al92Sm8 measured by fluctuation electron microscopy

Crystallization kinetics of Al86Ni8Gd6 amorphous alloy

Relation Between Medium-Range Order and Crystallization in Al-Ni Based Metallic Glass

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