Heterogeneously randomized STZ model of metallic glasses: Softening and extreme value statistics during deformation

Zhao, Pengyang; Li, Ju; Wang, Yunzhi

doi:10.1016/j.ijplas.2012.06.007

Cited by 79 publications

(36 citation statements)

References 68 publications

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“…SDT has the dual nature of "shear" and "diffusion", which is mathematically defined by an affine/non-affine decomposition of relative atomic displacements. As such, SDT is an extension of Argon and Eshelby's shear transformation concept 15,16 which emphasized the affine (shape change) part of stressdriven processes 17,20 . Previously, Delogu 38, 39 and Fujita et.al.…”

Section: Discussionmentioning

confidence: 99%

“…A shear-dominant tensorial stress τ lowers the barrier Q significantly 36 . Indeed, the activation volume-tensor Ω is defined by how sensitive Q is to stress: Ω≡−∂Q/∂τ 35 , and a large activation volume means the barrier Q(τ) comes down quickly with increasing shear stress applied 17,20,35 . With Q lowered, "menu options" pop up to allow the local configurations to be nudged towards lower-energy valleys.…”

Section: E Differences Between Lct and Deformation-induced Crystallimentioning

confidence: 99%

“…Here we report a mechanistic study of the crystallization process in an Al 50 Fe 50 MG, under cyclic loading in molecular dynamics(MD) simulations 12 .A fatigue crack with appropriate geometry under cyclic loading was used, which would not generate a cross-sample large shear band 18 that may create temperature rise 19 and other complications 17,20 . This geometry also gives rise to locations close to the crack tip, where the stress is amplified to accelerate the crystallization in local regions within the limited simulation time.…”

Section: Introductionmentioning

confidence: 99%

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Stress-driven crystallization via shear-diffusion transformations in a metallic glass at very low temperatures

Mao

et al. 2015

Phys. Rev. B

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At elevated temperatures, glasses crystallize via thermally activated diffusion.However, metallic glasses can also undergo deformation-induced crystallization at very low temperatures. Here we demonstrate the crystallization of Al 50 Fe 50 metallic glasses under cyclic deformation at 50 K using molecular dynamics simulations, and reveal the underlying atomic-scale processes. We demonstrate that stress-driven nonaffine atomic rearrangements, or shear diffusion transformation (SDT) events, lead to successive metabasin-to-metabasin transitions and long-range ordering. We also illustrate that the nucleation and growth of the crystal proceed via collective attachment of ordered clusters, advancing the amorphous/crystal interface in an intermittent manner. The cooperative nature of the step-like crystallization is attributed to the large activation volume of Eshelby transformations which generate as a byproduct non-affine "diffusive" atomic displacements that accumulate over loading cycles. The dual nature of "shear" (affine) and "diffusion" (non-affine) in lowtemperature stress-driven SDT events thus unifies inelasticity with crystallization.

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Section: Discussionmentioning

confidence: 99%

Section: E Differences Between Lct and Deformation-induced Crystallimentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Stress-driven crystallization via shear-diffusion transformations in a metallic glass at very low temperatures

Mao

et al. 2015

Phys. Rev. B

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“…While the analogy between the formation of "dislocation-free" grains and phase transformation has been adopted to intuitively explain the softening of DRX, it has to be noted that DRX is essentially related to the formation and migration of grain boundaries, which are extended defects rather than phases, and extended defects are strongly driven by stress rather than thermodynamics (Zhao et al, 2013(Zhao et al, , 2014. At the length scale of discrete extended defects, the RVE-average stress is expected to exhibit successive drops due to the repeated relaxation of local stresses, which, however, may easily be averaged out from further coarse-graining at a larger length scale.…”

Section: Softening During Drxmentioning

confidence: 99%

An integrated full-field model of concurrent plastic deformation and microstructure evolution: Application to 3D simulation of dynamic recrystallization in polycrystalline copper

Zhao

Low

Wang

et al. 2016

International Journal of Plasticity

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106

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Many time-dependent deformation processes at elevated temperatures produce significant concurrent microstructure changes that can alter the mechanical properties in a profound manner. Such microstructure evolution is usually absent in mesoscale deformation models and simulations. Here we present an integrated full-field modeling scheme that couples the mechanical response with the underlying microstructure evolution. As a first demonstration, we integrate a fast Fourier transform-based elasto-viscoplastic (FFT-EVP) model with a phase-field (PF) recrystallization model, and carry out three-dimensional simulations of dynamic recrystallization (DRX) in polycrystalline copper. A physics-based coupling between FFT-EVP and PF is achieved by (1) adopting a dislocation-based constitutive model in FFT-EVP, which allows the predicted dislocation density distribution to be converted to a stored energy distribution and passed to PF, and (2) implementing a stochastic nucleation model for DRX. Calibrated with the experimental DRX stress-strain curves, the integrated model is able to deliver full-field mechanical and microstructural information, from which quantitative description and analysis of DRX can be achieved. It is suggested that the initiation of DRX occurs significantly earlier than previous predictions, due to heterogeneous deformation. DRX grains are revealed to form at both grain boundaries and junctions (e.g., quadruple junctions) and tend to grow in a wedge-like fashion to maintain a triple line (not necessarily in equilibrium) with old grains. The resulting stress redistribution due to strain compatibility is found to have a profound influence on the subsequent dislocation evolution and softening.

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“…Studying Slow Dynamics -In order to study the slow dynamics in glassy materials 30 in general, we have developed a Markovian network model to calculate the shear viscosity of deeply supercooled liquids based on sampling of an atomistic energy landscape. Shear stress relaxation is calculated from a master-equation description in which the system follows a transition-state pathway trajectory of hopping among local energy minima separated by activation barriers, which is in turn sampled by accerlated MD-based algorithms 6 .…”

Section: Resultsmentioning

confidence: 99%

PECASE - First Principles Modeling of Mechanics and Chemistry of Materials

Li¹

2013

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Heterogeneously randomized STZ model of metallic glasses: Softening and extreme value statistics during deformation

Cited by 79 publications

References 68 publications

Stress-driven crystallization via shear-diffusion transformations in a metallic glass at very low temperatures

Stress-driven crystallization via shear-diffusion transformations in a metallic glass at very low temperatures

An integrated full-field model of concurrent plastic deformation and microstructure evolution: Application to 3D simulation of dynamic recrystallization in polycrystalline copper

PECASE - First Principles Modeling of Mechanics and Chemistry of Materials

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