Coupled strain-induced alpha to omega phase transformation and plastic flow in zirconium under high pressure torsion in a rotational diamond anvil cell

Feng, Biao; Levitas, Valery I.; Kamrani, Mehdi

doi:10.1016/j.msea.2018.06.061

Cited by 25 publications

(19 citation statements)

References 39 publications

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“…52, 53, 7377); contact sliding utilizing combined Coulomb and plastic friction was introduced in Refs. 17,67,68,72). Here, we will present some recent simulations for plastic strain-induced ¡ ¼ ½ transformation in zirconium under torsion in rotational diamond anvils.…”

Section: Modeling Of Plastic Flowmentioning

confidence: 99%

“…Initially, within an oversimplified elastic model, it was explained by an increase in the elastic moduli during the PT. 7) However, more adequate analytical plastic solutions 24,25,72) suggested that the higher yield strength of the HPP and reduction in sample thickness during torsion, compensating for transformational volume decrease, are responsible for this effect. This was later confirmed by a much more detailed FEM solution.…”

Section: Modeling Of Plastic Flowmentioning

confidence: 99%

“…77). However, all high-pressure torsion experiments 10,11,72) use the averaged pressure for this purpose. Based on FEM results, such an averaged pressure should be corrected by a factor of 2.2 for strain-induced ¡ ¼ ½ transformation and by a factor of 5 for strain-induced ½ ¼ ¢ transformation to obtain a correct estimate for p d ¾ ; see Ref.…”

Section: Modeling Of Plastic Flowmentioning

confidence: 99%

“…Based on FEM results, such an averaged pressure should be corrected by a factor of 2.2 for strain-induced ¡ ¼ ½ transformation and by a factor of 5 for strain-induced ½ ¼ ¢ transformation to obtain a correct estimate for p d ¾ ; see Ref. 72). All previous limitations of the model in Refs.…”

Section: Modeling Of Plastic Flowmentioning

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: Modeling Of Plastic Flowmentioning

confidence: 99%

Section: Modeling Of Plastic Flowmentioning

confidence: 99%

Section: Modeling Of Plastic Flowmentioning

confidence: 99%

Section: Modeling Of Plastic Flowmentioning

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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“…Strong effects of grain size on the PTs in Ti (Edalati et al, 2014) and TiO2 ceramics (Razavi-Khosroshahi et al, 2016) were observed experimentally. Because the pressure was estimated as force per area in the above works with anvils made of hard alloys, significant corrections due to pressure heterogeneity were suggested in Feng and Levitas (2017c) and Feng et al (2018b). From experiment and simulation, Feng et al (2018c) found that PT and twinning are strongly strain-rate-and loading-orientationdependent.…”

Section: Introductionmentioning

confidence: 99%

FEM modeling of plastic flow and strain-induced phase transformation in BN under high pressure and large shear in a rotational diamond anvil cell

Feng

Levitas

2019

International Journal of Plasticity

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Combined three-dimensional plastic flow and strain-induced phase transformation (PT) in boron nitride (BN) under high pressure and large shear in a rotational diamond anvil cell (rotational DAC or RDAC) are investigated. Geometrically nonlinear frameworks including finite elastic, transformational, and plastic deformations and finite element method (FEM) are utilized. Quantitative information is obtained on the evolutions of the stress tensor, plastic strain, volume fraction of phases in the entire sample, and slip-cohesion transitions, all during torsion under a fixed compressive load in RDAC. The effects of the applied compressive stress and the sample radius on PT and plastic flow are discussed. In comparison with DAC, the same amount of the high-pressure phase can be obtained at a much lower pressure in RDAC, which reduces the required force and the risk of diamond fracture. Also, RDAC has a potential to complete PT during torsion under pressure close to the minimum possible. A quasi-homogeneous pressure can be obtained in a transforming sample in RDAC under a proper choice of properties and parameters of a gasket. A number of experimental phenomena, including the pressure self-multiplication and quasi-homogeneous pressures in DAC and RDAC, are reproduced and interpreted. The simulation results provide a significant insight into coupled PTs and plastic flow in material in RDAC, and are important for the optimum design of experiments and the extraction of material parameters for PT, as well as for the optimization and control of PTs by the variation of various parameters.

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In situ quantitative study of plastic strain-induced phase transformations under high pressure: Example for ultra-pure Zr

Pandey

Levitas

2020

Acta Materialia

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Coupled strain-induced alpha to omega phase transformation and plastic flow in zirconium under high pressure torsion in a rotational diamond anvil cell

Cited by 25 publications

References 39 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

FEM modeling of plastic flow and strain-induced phase transformation in BN under high pressure and large shear in a rotational diamond anvil cell

In situ quantitative study of plastic strain-induced phase transformations under high pressure: Example for ultra-pure Zr

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