Structural Aspects of Metallic Glasses

Miracle, D.B.; Egami, T.; Flores, Katharine M.; Kelton, K. F.

doi:10.1557/mrs2007.124

Cited by 172 publications

(97 citation statements)

References 68 publications

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“…In this paper, we apply stress relaxation method covering a wide temperature range and dynamical mechanical analysis, which can detect the b-relaxation to investigate the evolution process of GLT in MG, which can be simply treated as random stacking of hard spheres [31][32][33] . A La 60 Ni 15 Al 25 MG, with excellent glass-forming ability, thermal stability and unusual pronounced b-relaxation behaviour among known MGs 34,35 , is chosen as a model system.…”

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Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

et al. 2014

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For glasses, the structural origin of their flow phenomena, such as elastic and plastic deformations especially the microscopic hidden flow before yield and glass-to-liquid transition (GLT), is unclear yet due to the lack of structural information. Here we investigate the evolution of the microscopic localized flow during GLT in a prototypical metallic glass combining with dynamical mechanical relaxations, temperature-dependent tensile experiments and stress relaxation spectra. We show that the unstable and high mobility nano-scale liquid-like regions acting as flow units persist in the glass and can be activated by either temperature or external stress. The activation of such flow units is initially reversible and correlated with b-relaxation. As the proportion of the flow units reaches a critical percolation value, a mechanical brittle-to-ductile transition or macroscopic GLT happens. A comprehensive picture on the hidden flow as well as its correlation with deformation maps and relaxation spectrum is proposed.

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confidence: 99%

Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

et al. 2014

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“…However, the latest finding indicated that the MRO in MGs can be described by packing of quasiequivalent clusters on a fractal network with a dimension (D f ) of 2.31 [14], implying that it is impossible to fill the real space in these amor phous solids by building blocks in a form of crystal (D f ¼ 3:0) or icosahedral-quasicrystal (D f ¼ 2:72) symmetry. The nature of atomic packing at the MRO scale or larger in MGs still remains mysterious [15].Glassy alloys are commonly considered as the state of ''frozen liquids''; nevertheless, their structure difference is obvious: A split in the second peak of the atomic-pair distribution function (PDF) curve, gðrÞ, for MGs, occurs with respect to that for liquids. Actually, the splitting of the second maximum of the gðrÞ curve into two subpeaks is recognized as a characteristic indication of amorphous solids [16], and its origin has been investigated extensively [17][18][19].…”

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Metallic Liquids and Glasses: Atomic Order and Global Packing

et al. 2010

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In this Letter, we have revealed the common structural behavior of metallic glasses through scrutinizing the evolution of pair distribution functions from metallic liquids to glasses and statistically analyzing pair distribution functions of 64 metallic glasses. It is found that the complex atomic configuration in metallic glasses can be interpreted globally as a combination of the spherical-periodic order and local translational symmetry. The implications of our study suggest that the glass transition could be visualized mainly as a process involving in local translational symmetry increased from the liquid to glassy states. DOI: 10.1103/PhysRevLett.105.155501 PACS numbers: 61.43.Dq, 61.43.Bn The atomic structure of metallic glasses (MGs) is a fundamental and intriguing issue in condensed-matter physics, due to its importance in understanding the glassforming mechanism and unique properties [1][2][3][4]. Many structural models have been proposed over the years, such as ''dense random packing'' of hard spheres [5] and the ''stereochemically designed '' model [6]. Although these early models significantly improved our understanding of atomic structures in MGs, especially for short-range order (SRO), they still have their own insufficiencies [7]. Recent studies confirm that the characteristics of medium-range order (MRO) clusters dictate the stability and mechanical properties of monolithic MGs [8][9][10][11], which have shed new light on our understanding of structural features at this length scale [7,[12][13][14]. By taking the earlier models further with advances in relevant experimental techniques and computational capacity, the idealized cluster packing schemes, such as efficient cluster packing on a facecentered cubic (fcc) lattice [12] and quasiequivalent clusters on an icosahedral packing [7], have been proposed and furthered our comprehension of the MRO. However, the latest finding indicated that the MRO in MGs can be described by packing of quasiequivalent clusters on a fractal network with a dimension (D f ) of 2.31 [14], implying that it is impossible to fill the real space in these amor phous solids by building blocks in a form of crystal (D f ¼ 3:0) or icosahedral-quasicrystal (D f ¼ 2:72) symmetry. The nature of atomic packing at the MRO scale or larger in MGs still remains mysterious [15].Glassy alloys are commonly considered as the state of ''frozen liquids''; nevertheless, their structure difference is obvious: A split in the second peak of the atomic-pair distribution function (PDF) curve, gðrÞ, for MGs, occurs with respect to that for liquids. Actually, the splitting of the second maximum of the gðrÞ curve into two subpeaks is recognized as a characteristic indication of amorphous solids [16], and its origin has been investigated extensively [17][18][19]. For example, Bennett proposed that the first subpeak at R 2 =R 1 ¼ ffiffiffi 3 p results from a continuum of configuration of two coplanar equilateral triangles sharing a common side, and the second one at R 3 =R 1 ¼ ffiffiffi 4 p originat...

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“…Atomic structures in liquids are believed to have an intrinsic influence on the glass-forming ability (GFA) of alloy [1]. However, it is still hard to identify the structural mechanism responsible for the competition between crystallization and vitrification, as the characterization of the atomic-level structure in liquid and glass state is very challenging for experimental techniques, such as X-ray scattering which usually give a statistical result.…”

Section: Introductionmentioning

confidence: 99%

“…However, it is still hard to identify the structural mechanism responsible for the competition between crystallization and vitrification, as the characterization of the atomic-level structure in liquid and glass state is very challenging for experimental techniques, such as X-ray scattering which usually give a statistical result. Despite this, structural studies have ascribed the high GFA to a complicated dense random packed structure, which lead to high viscosity of the supercooled liquid state and slow crystallization [1][2][3][4]. The select of multicomponents on bulk metallic glass (BMG) formation is concluded as 'a principal confusion' [5].…”

Section: Introductionmentioning

confidence: 99%

“…Atomic packing involves some geometrical parameters, such as atomic size difference and size of clusters, while atomic bonding is more related to the electronic structures. It is still unclear that the effect of compositional complexity on structure is purely topological [1,17] or is strongly influenced by the intricate bonding environments [4,18].…”

Section: Introductionmentioning

confidence: 99%

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Study on crystallization kinetics of binary alloys through model colloidal mixtures

Ding

Dai

et al. 2010

Journal of Alloys and Compounds

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a b s t r a c tSince the discovery of amorphous alloys, extensive attentions have been paid to understand the mechanism of glass-forming. The structural studies on its underlying mechanism have met challenge on direct structural characterization. It has been shown that the phase behavior of colloids dispersed in a solvent is thermodynamically equivalent to that of atoms and small molecules, however, colloids can be studied with optical microscopy due to their relatively large size. In this work, we use a binary colloidal model system with the particle size ratio comparable to atomic ratio of reported binary bulk metallic glasses to study the topological effect on crystallization and glass-forming ability of binary metallic alloys (Cu-Hf and Cu-Zr systems). The crystallization kinetics and structure of the colloid system were studied by realtime optical examination and light scattering technique. The results exhibit that there are two confined regions in the mixing ratio (composition) range in the colloid system with an enhanced glass-forming ability and retarded crystallization kinetics. The agreement between results of the model system and the experimental data on the binary bulk metallic glass formation suggests that purely topological factor plays an important role in determining the glass-forming ability.

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Structural Aspects of Metallic Glasses

Cited by 172 publications

References 68 publications

Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

Evolution of hidden localized flow during glass-to-liquid transition in metallic glass

Metallic Liquids and Glasses: Atomic Order and Global Packing

Study on crystallization kinetics of binary alloys through model colloidal mixtures

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