Microscopic View of Structural Phase Transitions Induced by Shock Waves

Kadau, Kai; Germann, Timothy C.; Lomdahl, Peter S.; Holian, Brad Lee

doi:10.1126/science.1070375

Cited by 444 publications

(264 citation statements)

References 28 publications

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“…Correspondingly, Maki and Tamura 14 found that with increasing Ni and C the reversibility of the phase changes increased, the amount of plastic deformation decreased, and the morphology changed from lath to butterfly to lenticular to plate-like. Iron also undergoes a pressure-induced reconstructive α-ε (bcc to hexagonal-close-packed, hcp) transformation, again accompanied by both twins and dislocations 15,16 . Another set of observations concern materials undergoing the reconstructive fcc-to-hcp transformation.…”

Section: -09-09210bmentioning

confidence: 99%

Crystal symmetry and the reversibility of martensitic transformations

Bhattacharya

Conti

Zanzotto

et al. 2004

Nature

313

201

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§ All authors contributed equally to this work.Martensitic transformations are diffusionless solid-to-solid phase transitions characterized by a rapid change of crystal structure, observed in metals, alloys, ceramics, and proteins 1,2 . Phenomenologically, they come in two widely different classes. In steels, quenching generates a microstructure which remains essentially unchanged upon subsequent loading or heating; the transformation is not reversible 1 . In shape-memory alloys on the other hand the microstructures formed on cooling are easily manipulated by loads and disappear upon reheating, and the transformation is reversible 3,4 . Here we explain these sharp differences on the basis of the change in crystal symmetry during the transition. In particular, we show that martensitic transformations fall into two categories. In one case the energy barrier to plastic deformation (via lattice-invariant shears, as in twinning or slip) is no higher than the barrier to the phase change itself. These transformations are therefore irreversible, as observed in steels. In the other case, the energy barrier to lattice-invariant shears can be much higher than that pertaining to the phase change. Consequently, transformations of this type can occur with virtually no plasticity and can be reversible, as for shape-memory alloys.Martensitic transformations are at the basis of numerous technological applications. Most notable amongst these is in steel, where the transformation induced by quenching (fast cooling) is exploited for enhancing the alloy's strength 1 . Another is the fascinating shape-memory effect in alloys like Nitinol, used in medical and engineering devices 3 . Martensitic phase changes are also exploited to toughen structural ceramics 5 such as zirconia, and observed in biological systems such as the tail sheath of the T4 bacteriophage virus 6 . Ideas originating from the study of these transformations have led to improved materials for actuation (ferromagnetic shape-memory alloys 7,8 and ferroelectrics 9 ) and to candidates for artificial muscles 10 . Finally, the rich microstructure (distinctive patterns developed at scales ranging from a few nanometers to a few microns) that accompanies these transformations, has made this a valuable theoretical sand-box for the development of multi-scale modeling tools 11 .

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Section: -09-09210bmentioning

confidence: 99%

Crystal symmetry and the reversibility of martensitic transformations

Bhattacharya

Conti

Zanzotto

et al. 2004

Nature

313

201

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“…For example, large scale molecular dynamics simulations by Kadau et.al. [39] predict crystalline phase transitions in metals induced by the passage of a shock wave. Now, using FEL sources it should be possible to image such transitions as they occur in time-resolved diffraction experiments.…”

Section: Perspectives On the Future: Lcls Xfel And Beyondmentioning

confidence: 99%

Time-resolved imaging using x-ray free electron lasers

Barty

2010

J. Phys. B: At. Mol. Opt. Phys.

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The ultra-intense, ultra-short X-ray pulses provided by X-ray Free Electron Laser (XFEL) sources are ideally suited to time resolved studies of structural dynamics with spatial resolution from nanometre to atomic length scales and temporal resolution of 10 fs or less. Using coherent X-ray diffraction as a diagnostic, XFELs enable the capturing of X-ray snapshots of previously unmeasurable transient phenomena, and the study of ultrafast processes such as sample damage on the timescales which they occur. With enough photons in a single pulse to enable single-shot measurements, and short enough pulses to freeze atomic motion, researchers now have a new window into the time evolution ultrafast phenomena that are intrinsically not cyclic in nature. In this review paper we recap some of the key time-resolved imaging experiments performed at FLASH and look ahead to a new generation of experiments at higher resolution using a new generation of new XFEL sources that are only just becoming available.

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“…MD has been used extensively to study shock compression mechanisms which require the resolution of atomistic detail [14,15], and is especially useful when heterogeneity [16,17] requires domain sizes too large for density functional theory (QMD-DFT). Sandia's LAMMPS code [18] was used with the Modified Embedded Atom Method (MEAM) [19] and silicon parameters distributed in LAMMPS as Si97 within library.meam [20,21].…”

Section: Methodsmentioning

confidence: 99%

Enhanced densification under shock compression in porous silicon

2014

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Under shock compression, most porous materials exhibit lower densities for a given pressure than that of a full-dense sample of the same material. However, some porous materials exhibit an anomalous, or enhanced, densification under shock compression. We demonstrate a molecular mechanism that drives this behavior. We also present evidence from atomistic simulation that pure silicon belongs to this anomalous class of materials. Atomistic simulations indicate that local shear strain in the neighborhood of collapsing pores nucleates a local solid-solid phase transformation even when bulk pressures are below the thermodynamic phase transformation pressure. This metastable, local, and partial, solid-solid phase transformation, which accounts for the enhanced densification in silicon, is driven by the local stress state near the void, not equilibrium thermodynamics. This mechanism may also explain the phenomenon in other covalently bonded materials.

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Microscopic View of Structural Phase Transitions Induced by Shock Waves

Cited by 444 publications

References 28 publications

Crystal symmetry and the reversibility of martensitic transformations

Crystal symmetry and the reversibility of martensitic transformations

Time-resolved imaging using x-ray free electron lasers

Enhanced densification under shock compression in porous silicon

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