Phase Transitions in Solids Under High Pressure

Blank, V. D.; Éstrin, É. I.

doi:10.1201/b15943

Cited by 65 publications

(128 citation statements)

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“…At pressures of 1.59 and 5 GPa and shear, a major part of a grain transforms to HPP. This conceptually proves that the dislocation pile-up mechanism is able to reduce PT pressure due to applied shear by an order of magnitude, as it was observed in experiments [6,93,96,114]. When dislocations in the right grain are included, they relax stress concentration, which reduces stresses, the driving force for PT and, consequently, HPP concentration.…”

Section: Discussionmentioning

confidence: 53%

“…A new high-density amorphous phase of SiC was observed in situ under pressure of 30 GPa and large shear [88] but no PTs were obtained under hydrostatic pressure up to 130 GPa. There are many examples that show that application of shear reduces PT pressure by a factor of 2 to 10 for some PTs [6,85,90,93,95,96,97,98,99,103], including PTs to superhard phases of BN [90,95], PTs in Si and Ge [85,96], and Zr and Zr-Nb alloys [97,98]. An important point is that some of these discoveries at relatively low pressure can be scaled up using high pressure torsion [97,98,100,101,102,99,103] and ball milling [104,105,106,107,108,109,110].…”

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

“…Problem formulation in [64] considers the superposition of shear strain on a constrained uniaxial compression, even though the main discussion is on how shear reduces the PT pressure. In fact, the uniaxial compression reduces the PT pressure in comparison with hydrostatic conditions without shear, see, e.g., [91,94,96,99]. Alternative boundary conditions-free lateral surfaces-, have been applied for an exploratory study of the shearinduced PT at zero pressure in [8].…”

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

“…Bridgman anvils [84] or rotational diamond anvil cell (RDAC) [85,86,87,88,89,90,92,93,95,96], can lead to new phases that were not obtained under hydrostatic conditions and significantly reduces PT pressure. For example, a superhard phase IV of fullerene C 60 [89,90] and single wall carbon nanotube [92] as well as highly energetic phases of nitrogen and sodium azide [86,87] were discovered under compression and shear in RDAC.…”

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

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Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Javanbakht

Levitas

2016

Phys. Rev. B

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Pressure and shear strain-induced phase transformations (PTs) in a nanograined bicrystal at the evolving dislocations pile-up have been studied utilizing phase field approach (PFA).The complete system of PFA equations for coupled martensitic PT, dislocation evolution, and mechanics at large strains is presented and solved using finite element method (FEM). The nucleation pressure for high pressure phase (HPP) under hydrostatic condition near single dislocation was determined to be 15.9 GPa. Under shear, a dislocations pile-up that appears in the left grain creates strong stress concentration near its tip and significantly increases the local thermodynamic driving force for PT, which causes nucleation of HPP even at zero pressure. At pressures of 1.59 and 5 GPa and shear, a major part of a grain transforms to HPP.When dislocations are considered in the transforming grain as well, they relax stresses and lead to a slightly smaller stationary HPP region than without dislocations. However, they strongly suppress nucleation of HPP and require larger shear. Unexpectedly, the stationary HPP morphology is governed by the simplest thermodynamic equilibrium conditions, which do not contain contributions from plasticity and surface energy. These equilibrium conditions are fulfilled either for the majority of points of phase interfaces or (approximately) in terms of stresses averaged over the HPP region or for the entire grain, despite the strong heterogeneity of stress fields. The major part of the driving force for PT in the stationary state is due to deviatoric stresses rather than pressure. While the least number of dislocations in a pile-up to nucleate HPP linearly decreases with increasing the applied pressure, the least corresponding shear strain depends on pressure nonmonotonously. Surprisingly, the ratio of kinetic coefficients for PT and dislocations affect stationary solution and nanostructure. Consequently, there are multiple stationary solutions under the same applied load and PT and deformation processes are path dependent. With an increase in the size of the sample by a factor of two, 2 no effect was found on the average pressure and shear stress and HPP nanostructure, despite the different number of dislocations in a pile-up. Obtained results represent a nanoscale basis for understanding and description of PTs under compression and shear in rotational diamond anvil cell and high pressure torsion.

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Section: Discussionmentioning

confidence: 53%

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

Section: Pts Under High Pressure and Compression And Shearmentioning

confidence: 99%

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Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Javanbakht

Levitas

2016

Phys. Rev. B

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“…These metals have been heavily investigated at high P-T conditions [1][2][3][4][5][6][7][8][9][10][11][12] due, in part, to their importance for technical applications. In particular, zirconium is important as a component of nuclear reactors and is widely used for neutron work due to the low neutron cross-section.…”

Section: Introductionmentioning

confidence: 99%

Pressure-induced kinetics of the α to ω transition in zirconium

Jacobsen

Velisavljevic

Sinogeikin

2015

Journal of Applied Physics

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Diamond anvil cells (DAC) coupled with x-ray diffraction (XRD) measurements are one of the primary techniques for investigating structural stability of materials at high pressure-temperature (P-T) conditions. DAC-XRD has been predominantly used to resolve structural information at set P-T conditions and, consequently, provides P-T phase diagram information on a broad range of materials. With advances in large scale synchrotron x-ray facilities and corresponding x-ray diagnostic capabilities, it is now becoming possible to perform sub-second time resolved measurements on micron sized DAC samples. As a result, there is an opportunity to gain valuable information about the kinetics of structural phase transformations and extend our understanding of material behavior at high P-T conditions. Using DAC-XRD time resolved measurements, we have investigated the kinetics of the α to ω transformation in zirconium. We observe a clear time and pressure dependence in the martensitic α-ω transition as a function of pressure-jump, i.e., drive pressure. The resulting data are fit using available kinetics models, which can provide further insight into transformation mechanism that influence transformation kinetics. Our results help shed light on the discrepancies observed in previous measurements of the α-ω transition pressure in zirconium.

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Review on Recent Advancements in Severe Plastic Deformation of Oxides by High‐Pressure Torsion (HPT)

Edalati

2018

Adv Eng Mater

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Severe plastic deformation (SPD) of oxides has been of interest in mineralogy and geology for many decades, but oxides have ionic or covalent bonds with brittle nature and can hardly be deformed at ambient temperature. SPD processing of oxides is first realized in 1930s, when Percy W. Bridgman introduce the principles of high-pressure torsion (HPT) method. Although the method is widely used nowadays to produce ultrafine-grained (UFG) metals, the application of method for SPD processing of oxides is quite limited. This article reviews some of the recent publications on the application of HPT method to oxide ceramics () and summarizes their major findings: powder compaction and partial consolidation, nanograin formation, formation of different kinds of lattice defects such as dislocations and oxygen vacancies, strain and grain size dependence of phase transformations, and improvement of functional properties such as bandgap narrowing, photoluminescence, photocatalytic activity, and dielectricity. Early Studies on HPT Processing of OxidesAs mentioned earlier, SPD processing of oxides has been of interest for many decades in mineralogy and geology. Boeker is

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Phase Transitions in Solids Under High Pressure

Cited by 65 publications

References 0 publications

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Phase field simulations of plastic strain-induced phase transformations under high pressure and large shear

Pressure-induced kinetics of the α to ω transition in zirconium

Review on Recent Advancements in Severe Plastic Deformation of Oxides by High‐Pressure Torsion (HPT)

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