Unusual energy state evolution in Ce-based metallic glass under high pressure

Ge, T. P.; Wang, C.; Tan, Jieqing; Ma, Tianxing; Xin, Yu; Jin, Chao; Wang, W. H.; Bai, H. Y.

doi:10.1063/1.4983017

Cited by 15 publications

(5 citation statements)

References 71 publications

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“…Under high pressure, the atoms become densely packed with an increased density, and the annihilation of flow units follows in a similar manner to thermal annealing, but is more effective by pressure. After adjusting the pressure level and further combining with thermal annealing, high energy was successfully stored and preserved in bulk MG samples, and the energy states can be continuously altered using this approach [ 134 , 135 ]. The rejuvenation attributed to the coupling effect of high pressure and high temperature leads to unique structural heterogeneity that contains ‘negative flow units’, with a higher atomic packing density compared to that of the elastic matrix of MGs [ 134 ].…”

Section: Property Optimization Based On the Flow Unit Perspectivementioning

confidence: 99%

Flow units as dynamic defects in metallic glassy materials

Wang

2018

National Science Review

115

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In a crystalline material, structural defects such as dislocations or twins are well defined and largely determine the mechanical and other properties of the material. For metallic glass (MG) with unique properties in the absence of a long-range lattice, intensive efforts have focused on the search for similar ‘defects’. The primary objective has been the elucidation of the flow mechanism of MGs. However, their atomistic mechanism of mechanical deformation and atomic flow response to stress, temperature, and failure, have proven to be challenging. In this paper, we briefly review the state-of-the-art studies on the dynamic defects in metallic glasses from the perspective of flow units. The characteristics, activation and evolution processes of flow units as well as their correlation with mechanical properties, including plasticity, strength, fracture, and dynamic relaxation, are introduced. We show that flow units that are similar to structural defects such as dislocations are crucial in the optimization and design of metallic glassy materials via the thermal, mechanical and high-pressure tailoring of these units. In this report, the relevant issues and open questions with regard to the flow unit model are also introduced and discussed.

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Section: Property Optimization Based On the Flow Unit Perspectivementioning

confidence: 99%

Flow units as dynamic defects in metallic glassy materials

Wang

2018

National Science Review

115

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“…Routes to homogeneously modify the glassy structure via mechanical stresses or thermomechanical loading have received increased attention. However, these studies do not yet allow constructing a general understanding of how stresses can drive the structure into a different energy state.…”

Section: Tuning Structure Homogeneously Via Thermal and Mechanical Prmentioning

confidence: 99%

“…The sensitivity of relaxation or rejuvenation to the stress state was discussed by Wang et al, who reported densification and hardening due to stress‐enhanced relaxation under a multiaxial stress state, underlining that the homogeneous structural evolution due to stresses of an MG may be sensitive to a number of boundary conditions that are yet to be identified. Another route is to subject an MG to high pressure in combination with sub‐ T g annealing, thermomechanical creep, or to apply isotropic hydrostatic pressure . The latter method showed to rejuvenate the glass, but at the same time the hardness increased as well, which is at odds with the general opinion that rejuvenation causes a density and hardness reduction.…”

Section: Tuning Structure Homogeneously Via Thermal and Mechanical Prmentioning

confidence: 99%

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Elastic Fluctuations and Structural Heterogeneities in Metallic Glasses

Liu

Maaß

2018

Adv Funct Materials

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Suppressing crystallization of a metallic melt results in a disordered solid, also known as a metallic glass. One may conclude that a metallic glass is free of defined structural length scales beyond some atomic-scale value that characterizes short-and medium-range order. While it is well known from atomistic modeling that a metallic glass is structurally heterogeneous, heterogeneities at such a small length scale can hardly be resolved in experiments. This review highlights experimental insights into elastic fluctuations and structural heterogeneities that emerge at scales between a few nanometers and tens to hundreds of micrometers. It distinguishes between structural and property fluctuations in as-cast metallic glasses, and heterogeneities introduced by elastic and inhomogeneous plastic deformation. As-cast glasses reveal elastic fluctuations across 3 orders of magnitude, suggesting a hierarchy of length scales that can be tuned by thermomechanical processing. Similarly, nanoscale strain localization into shear bands drives the formation of structural and elastic heterogeneities at both the nano-and the microscale. It is proposed that both types of fluctuations will allow one to quantitatively define structure-property relationships via measurable length scales-an approach that has largely contributed to the engineering success of crystalline metals.

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“…Rejuvenation of metallic glasses is usually associated with increased disorder, excess free volume (or lower density), increase plasticity and toughness, and reduced hardness and strength 9,13 . However, some rejuvenation processes involving deformation protocols and thermal treatments have revealed increases in density and hardness in some metallic glasses [14][15][16] . The observed strain-hardening behavior in these alloys following treatment had been associated with confined microplasticity and local accumulation of irreversible compressive strains 17,18 .…”

Section: Introductionmentioning

confidence: 99%

Rejuvenation engineering in metallic glasses by complementary stress and structure modulation

Şopu

Spieckermann

Fellner

et al. 2023

Preprint

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Residual stress engineering is very widely used in the design of new advanced lightweight materials. For metallic glasses the attention has been on structural changes and rejuvenation processes. High energy scanning X-ray diffraction strain mapping reveals large elastic fluctuations in notched metallic glasses after deformation under triaxial compression. Microindentation hardness mapping hints to a competing hardening-softening mechanism after compression and further reveals the complementary effects of stress and structure modulation. Transmission electron microscopy proves that structure modulation and the distribution of elastic heterogeneities under room temperature deformation relates to the shear band formation. Molecular dynamics simulations provide an atomistic understanding of the confined deformation mechanism in notched metallic glasses and the related fluctuations in the elastic and plastic strains. Thus, future focus should be given to stress modulation and elastic heterogeneity that together with structure modulation may allow to design metallic glasses with enhanced ductility and strain hardening ability.

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Unusual energy state evolution in Ce-based metallic glass under high pressure

Cited by 15 publications

References 71 publications

Flow units as dynamic defects in metallic glassy materials

Flow units as dynamic defects in metallic glassy materials

Elastic Fluctuations and Structural Heterogeneities in Metallic Glasses

Rejuvenation engineering in metallic glasses by complementary stress and structure modulation

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