Lattice instability during phase transformations under multiaxial stress: Modified transformation work criterion

Levitas, Valery I.; Chen, Hao; Xiong, Liming

doi:10.1103/physrevb.96.054118

Cited by 44 publications

(65 citation statements)

References 36 publications

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“…This seemed to be impossible due to the large number of combinations, but unexpected guidance came from the PT criterion analytically formulated within the large-strain phase field approach (PFA) 33) under action of all six stresses · ij . Molecular dynamics simulations 34,35) and the first-principle simulations 36) were then performed to find lattice instability conditions for cubic-totetragonal PT between diamond cubic phase Si I and metallic phase Si II, in both directions. The results for Si I ¼ Si II PT obtained with molecular dynamics and first-principle simulations are quite close.…”

Section: Crystal Lattice Instability Criteria: Phase Fieldmentioning

confidence: 99%

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High-Pressure Phase Transformations under Severe Plastic Deformation by Torsion in Rotational Anvils

Levitas

2019

Mater. Trans.

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Numerous experiments have documented that combination of severe plastic deformation and high mean pressure during high-pressure torsion in rotational metallic, ceramic, or diamond anvils produces various important mechanochemical effects. We will focus here on four of these: plastic deformation (a) significantly reduces pressure for initiation and completion of phase transformations (PTs), (b) leads to discovery of hidden metastable phases and compounds, (c) reduces PT pressure hysteresis, and (d) substitutes a reversible PT with irreversible PT. The goal of this review is to summarize our current understanding of the underlying phenomena based on multiscale atomistic and continuum theories and computational modeling. Recent atomistic simulations provide conditions for initiation of PTs in a defect-free lattice as a function of the general stress tensor. These conditions (a) allow one to determine stress states that significantly decrease the transformation pressure and (b) determine whether the given phase can, in principle, be preserved at ambient pressure. Nanoscale mechanisms of phase nucleation at plastic-strain-induced defects are studied analytically and by utilizing advanced phase field theory and simulations. It is demonstrated that the concentration of all components of the stress tensor near the tip of the dislocation pileup may decrease nucleation pressure by a factor of ten or more. These results are incorporated into the microscale analytical kinetic equation for strain-induced PTs. The kinetic equation is part of a macroscale geometrically-nonlinear model for combined plastic flow and PT. This model is used for finite-element simulations of plastic deformations and PT in a sample under torsion in a rotational anvil device. Numerous experimentally-observed phenomena are reproduced, and new effects are predicted and then confirmed experimentally. Combination of the results on all four scales suggests novel synthetic routes for new or known high-pressure phases (HPPs), experimental characterization of strain-induced PTs under high-pressure during torsion under elevated pressure.

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Section: Crystal Lattice Instability Criteria: Phase Fieldmentioning

confidence: 99%

“…Phase transformation criteria in terms of stress · 3 vs. · 1 = · 2 for direct (D) Si I-to-Si II and reverse (R) Si II-to-Si I phase transformations from the first-principle simulations and molecular dynamics simulations,34,35) as well as the metallization criterion from the first-principle simulations. This figure is reproduced with permission from Ref 36…”

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confidence: 99%

High-Pressure Phase Transformations under Severe Plastic Deformation by Torsion in Rotational Anvils

Levitas

2019

Mater. Trans.

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“…That is why the interpolation functions for A-M i transformations should not be invariant with respect to an exchange of phases, and should contain an additional material parameter to control this. Recent molecular dynamic simulations (Levitas et al (2017)) show that such a parameter is needed to satisfy the lattice instability conditions under multiaxial loading. Note that in all the previous models except in Levitas (2013a); Levitas and Preston (2002a,b), the interpolation functions do not possess any free material parameters.…”

Section: Mpfa-ivmentioning

confidence: 99%

Nanoscale multiphase phase field approach for stress- and temperature-induced martensitic phase transformations with interfacial stresses at finite strains

Basak

Levitas

2018

Journal of the Mechanics and Physics of Solids

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A thermodynamically consistent, novel multiphase phase field approach for stress-and temperature-induced martensitic phase transformations at finite strains and with interfacial stresses has been developed. The model considers a single order parameter to describe the austenite↔martensitic transformations, and another N order parameters describing N variants and constrained to a plane in an N-dimensional order parameter space. In the free energy model coexistence of three or more phases at a single material point (multiphase junction), and deviation of each variant-variant transformation path from a straight line have been penalized. Some shortcomings of the existing models are resolved. Three different kinematic models (KMs) for the transformation deformation gradient tensors are assumed: (i) In KM-I the transformation deformation gradient tensor is a is a linear function of the Bain tensors for the variants. (ii) In KM-II the natural logarithms of the transformation deformation gradient is taken as a linear combination of the natural logarithm of the Bain tensors multiplied with the interpolation functions. (iii) In KM-III it is derived using the twinning equation from the crystallographic theory. The instability criteria for all the phase transformations have been derived for all the kinematic models, and their comparative study is presented. A large strain finite element procedure has been developed and used for studying the evolution of some complex microstructures in nanoscale samples under various loading conditions. Also, the stresses within variant-variant boundaries, the sample size effect, effect of penalizing the triple junctions, and twinned microstructures have been studied. The present approach can be extended for studying grain growth, solidifications, para↔ferro electric transformations, and diffusive phase transformations.

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“…The lattice distortion is originated from inhomogeneous deformation of lattice caused by stress exerted on crystal, which is statistically originated from storage of elastic energy. Borrow the scenario of virtual melting in crystal, the elastic energy can be correlated with phase transition . The stretch‐induced melting leads to the formation of transient melt, which recrystallizes under the coupled effect of temperature and stress.…”

Section: Discussionmentioning

confidence: 99%

“…For nonpolymeric materials, elastic energy stored during deformation of crystal is successfully used to explain the stretch‐induced phase transition, which, however, has never been applied to semicrystalline polymers due to their peculiar viscoelastic nature. In fact, polymer crystals are essentially the same as inorganic materials, as both sharing long‐range order .…”

Section: Introductionmentioning

confidence: 99%

Stretch‐Induced Melting and Recrystallization of Polyethylene‐Plasticizer Film Studied by In Situ X‐Ray Scattering: A Thermodynamic Point of View

Chen

Zhang

Yao

et al. 2018

J Polym Sci B Polym Phys

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With in situ synchrotron radiation X-ray scattering, the structural alteration of polyethylene-plasticizer film during uniaxial stretching is studied at temperature far below melting point of crystal. By analyzing the evolution rule of structural parameters quantitatively, stretch-induced melting and recrystallization process is validated to be the underlying mechanism of plastic deformation for the system. The physical essence of stretch-induced melting is proved to be phase transition driven by elastic energy which originates from lattice deformation. Conversely, the recrystallization process is proved to be controlled by temperature; furthermore, the growth of lamellae during recrystallization is in perfect accordance with kinetic theory by Lauritzen and Hoffman. This study provides a quantitative understanding to the long-existing melting-recrystallization model from a thermodynamics point of view.

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Lattice instability during phase transformations under multiaxial stress: Modified transformation work criterion

Cited by 44 publications

References 36 publications

High-Pressure Phase Transformations under Severe Plastic Deformation by Torsion in Rotational Anvils

High-Pressure Phase Transformations under Severe Plastic Deformation by Torsion in Rotational Anvils

Nanoscale multiphase phase field approach for stress- and temperature-induced martensitic phase transformations with interfacial stresses at finite strains

Stretch‐Induced Melting and Recrystallization of Polyethylene‐Plasticizer Film Studied by In Situ X‐Ray Scattering: A Thermodynamic Point of View

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