<i>In situ</i>Synchrotron Study of Phase Transformation Behaviors in Bulk Metallic Glass by Simultaneous Diffraction and Small Angle Scattering

Wang, X.-L.; Almer, Jon; Liu, C. T.; Wang, Y. D.; Zhao, J. K.; Stoica, A. D.; Haeffner, D. R.; Wang, W. H.

doi:10.1103/physrevlett.91.265501

Cited by 104 publications

(64 citation statements)

References 30 publications

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“…3(a) shows the SAXS patterns of the as-cast Vit106a and Vit1 at room temperature, where the rise of the intensity IðqÞ at small scattering vector q is connected to the structure heterogeneity on medium length scale [24]. Similar patterns have also been observed in other metallic glasses [25,26]. Like in Fig.…”

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confidence: 68%

Heterogeneous dynamics of metallic glasses

et al. 2015

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a b s t r a c tHeterogeneous dynamics in the flow of supercooled metallic liquids are revealed as the oscillated mechanical response in compression and evidenced to be consistent with the range of medium length scales over which structural rearrangements occur detected by small angle X-ray scattering (SAXS) in heating from room temperature to the supercooled liquid region. This range of medium length scales is suggested to be the structural origin of the heterogeneous dynamics of metallic glasses.Ó 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.A non-equilibrium transition from fluidity to rigidity [1], i.e., jamming, prevails in a wide variety of disordered systems [2], including granular media [3], colloidal suspensions [4], molecular systems [5]. While the disordered liquid-like structure remains basically unchanged at the transition, further exploration of the phase space is precluded by the glasslike arrest of their dynamics [1,[6][7][8]. Approaching the jamming limit, the development of heterogeneous atomic dynamics in glasses [2,4,9] is indicated by the structure heterogeneity, i.e., coexistence of liquid-like and solid-like regions [10] of medium length scale (1-3 nm) [11,12]. In situ scattering investigations [13][14][15] have already revealed the critical role played by atomic rearrangements underlying the structure heterogeneity in the flow (i.e., unjamming) of metallic glasses [1]. However, the inherent liquid-like or solid-like local configurations do not correlate well with the heterogeneous atomic rearrangements [16,17], implying that a static view of the structure heterogeneity is not enough to recognize the arrest of dynamics in the fluidity-to-rigidity transition. Rather, unjamming (e.g., flow or glass-to-liquid transition of glasses) and the underlying dynamics would be crucial. In this work, the flow and structure of supercooled metallic liquids are respectively examined via uniaxial compression and in situ small angle X-ray scattering (SAXS) in heating. The range of medium length scales over which structural rearrangements occur observed in SAXS is suggested to be the structural origin of the heterogeneous dynamics of metallic glasses. were carefully prepared to ensure the two ends being parallel. The high temperature compressive stress-strain (SS) curves were obtained above each BMG's T g-end (the end of glass transition temperature) with a Zwick/Roell mechanical testing system. In situ SAXS tests with increasing temperature on Vit106a and Vit1 were conducted at beamline BL16B1 of Shanghai Synchrotron Radiation Facility with a photon energy of 10 keV (wavelength 1.24 Å) to monitor the amorphous structure evolution. Rods of 3 mm in diameter ofThe Fig. 1(a)respectively. All these BMGs show similar stress-strain (SS) r À e responses with increasing strain rates. For example, Fig. 1(a) shows the SS curves for Vit106a. With increasing strain rate, the SS curves change from the stress r increasing monotonously to a plateau at strain rate _ e of an order of 10 À3 s À1, t...

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confidence: 68%

Heterogeneous dynamics of metallic glasses

et al. 2015

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“…The core has an approximate composition Zr 2 M (see the last column of Table 1), where M ¼ (Ni, Cu), consistent with the crystalline phase identified by X-ray diffraction. [6,10] The composition of the shell is also close to Zr 2 M, with various amounts of Al, Ni, and Cu in place of M. The structure of the shell is most likely of Zr 2 Ni type as well, since no other crystalline phases were identified in the Xray diffraction pattern at this annealing temperature. Indeed, metastable Zr 2 Al can exist as several polymorphs, [17] one of which is isostructural with tetragonal Zr 2 Ni.…”

Section: Communicationmentioning

confidence: 94%

Nanoscale Solute Partitioning in Bulk Metallic Glasses

et al. 2009

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Fundamental understanding of composition variations and morphology in the nanoscale is essential to the design of advanced materials. Partial crystallization or devitrification of bulk metallic glasses (BMGs) results in novel microstructures, with high density (10 23 -10 24 m À3) nanocrystalline precipitates evenly distributed in a glassy matrix. These crystalline precipitates are known to impede the propagation of shear bands, and are promising candidates for improving the mechanical properties of BMG alloys. [1][2][3][4] However, it has been an experimental challenge to determine the fine structure of these precipitates, and no one technique can provide all the answers. In this paper, we report the experimental study of a multicomponent BMG alloy, Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 , utilizing several state-of-the-art characterization techniques. Nanoscale solute partitioning due to strong chemical order is revealed at unprecedented detail by a new wide-field atom probe. This level of details is crucial for understanding the interference peaks observed in small-angle X-ray and neutron scattering experiments, an unsolved mystery for over a decade. A core/shell structure is formed as a result of nanoscale solute partitioning, which poisons the growth and helps stabilize the nanocrystalline particles.Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 is a widely studied BMG with excellent glass forming ability.[5-11] Upon devitrification, crystalline precipitates of 10-20 nm diameter emerge, as evidenced by high-resolution transmission electron microscopy.[9] Moreover, Z-contrast imaging, a technique more sensitive to composition distribution, showed high densities of distinct crystalline particles of similar sizes but with fuzzy boundaries.[9] Nanoscale composition fluctuations have been detected by atom probe tomography (APT), and were attributed to nanocrystalline particles.[11] The structure of devitrified Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 has also been investigated by small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS). While microscopy reveals structural details in a restricted field of view or analysis volume, small-angle scattering yields the average structure over the scattering volume. SANS and SAXS profiles of Zr 52.5 Cu 17.9 Ni 14.6 Al 10 Ti 5 are both characterized by an interference peak. [8][9][10][11] However, there has been no satisfactory analysis of the experimental data that could identify the underlying structure. Although composition fluctuations due to spinodal decomposition can produce interference peaks, [12,13] no composition wave with a characteristic wavelength was detected experimentally. Instead, well-defined crystalline particles were reported by microscopy experiments. [9,11] Mathematically, the interference peak could also be generated by second-phase particles with a depleted diffusion zone. [14,15] However, experimental determination of the fine-scale composition variations in zirconium-based alloys is difficult with traditional voltage-pulsed APT, due to their poor el...

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“…As to now, in-situ observations of metallic glasses are mainly based on small angle scattering (SAS) [5] and transmission electron microscope (TEM) [6][7][8]. To induce phase transition, samples are reheated during SAS examination, while in TEM observation the interaction between the electron beam and the sample could stimulate or accelerate phase transitions.…”

Section: Introductionmentioning

confidence: 99%

Instability of nanoscale metallic particles under electron irradiation in TEM

Chen

Zhang

Xia

et al. 2016

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. The stability of nano metallic glass under electron beam in transmission electron microscope (TEM) was investigated. The most common voltage of TEM used in metallic materials characterization was either 200 kV or 300 kV. Both situations were investigated in this work. An amorphous metallic particle with a dimension of a few hundred nanometers was tested under 300 keV electron irradiation. New phase decomposed from the parent phase was observed. Moreover, a crystal particle with the same composition and dimension was tested under 200 keV irradiation. Decomposition process also occurred in this situation. Besides, crystal orientation modification was observed during irradiation. These results proved that the electron beam in TEM have an effect on the stability of nanoscale samples during long time irradiation. Atomic displacement was induced and diffusion was enhanced by electron irradiation. Thus, artifacts would be induced when a nanoscale metallic sample was characterized in TEM. IntroductionAmorphous alloys (metallic glasses) are non-equilibrium materials, which will process phase transformations when heated or mechanically forced. Crystallization is the most important phase transition of amorphous alloys. Crystallization is not only a question related to the service life of glass materials, but also a scientific question including glass transition process and nucleation and growth in glass state. There is another phase transition which is frequently found and gets more attention in metallic glasses, that is phase separation [1]. Phase separation is originated from the positive mixing enthalpy between atoms [1, 2]. It is found that metallic glasses show obvious different mechanical properties after phase separation occurs [3,4].In-situ observation is favored in phase transformation investigation. As to now, in-situ observations of metallic glasses are mainly based on small angle scattering (SAS) [5] and transmission electron microscope (TEM) [6][7][8]. To induce phase transition, samples are reheated during SAS examination, while in TEM observation the interaction between the electron beam and the sample could stimulate or accelerate phase transitions. Moreover, TEM can provide direct morphology observation. Thus, TEM is more convenient and useful than SAS. However, the energy of the electron beam should be more than mega-electron-volt (MeV) to induce crystallization in metallic glass [6][7][8]. On the contrary, it seems that 200~300 keV electron beam is safe for metallic samples to be characterized without extra artifacts.However, considering the size effect, small samples with large surface to volume (S/V) value may

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In situSynchrotron Study of Phase Transformation Behaviors in Bulk Metallic Glass by Simultaneous Diffraction and Small Angle Scattering

Cited by 104 publications

References 30 publications

Heterogeneous dynamics of metallic glasses

Heterogeneous dynamics of metallic glasses

Nanoscale Solute Partitioning in Bulk Metallic Glasses

Instability of nanoscale metallic particles under electron irradiation in TEM

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