Investigation of the Mechanism of Nanostructuring of Near-Surface Titanium Layers under the Influence of Nanosecond Laser Pulses

Tokmacheva-Kolobova, A. Yu.

doi:10.1134/s1063785021020139

Cited by 3 publications

(1 citation statement)

References 8 publications

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“…There are two variants of LSP differing in the duration of used laser pulses. The first variant is nanosecond LSP [1][2][3][4]. The second, relatively young, variant involves ultrashort (femtosecond and picosecond) laser pulses (fs-ps LSP) [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Melting of Titanium by a Shock Wave Generated by an Intense Femtosecond Laser Pulse

et al. 2022

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Laser shock peening with ultrashort laser pulses has been studied by hydrodynamic and atomistic simulations, as well as experimentally. It has been shown that, in contrast to traditional nanosecond pulses, ultrashort laser pulses allow one to increase the produced pressures by two or three orders of magnitude from 1–10 GPa to 1000 GPa (1 TPa). The physics of phenomena changes fundamentally because shock waves generating pressures exceeding the bulk modulus of a metal melt it. It has been shown for the first time that the shock melting depth at pressures about 1 TPa is an order of magnitude larger than the thickness of the melt layer caused by heat conduction. The appearance, propagation, and damping of a melting shock wave in titanium have been studied. The damping of the shock wave makes it possible to modify the surface layer, where the melting regime changes from a fast one in the shock jump to a slow propagation of the melting front in the unloading tail behind the shock wave. It has been shown experimentally that the ultrafast crystallization of the melt forms a solid layer with a structure strongly different from that before the action. The measured depth of this layer is in good agreement with the calculation.

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Section: Introductionmentioning

confidence: 99%

Melting of Titanium by a Shock Wave Generated by an Intense Femtosecond Laser Pulse

et al. 2022

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Shock-induced melting and crystallization in titanium irradiated by ultrashort laser pulse

Zhakhovsky,

Kolobov,

Ashitkov

et al. 2023

Physics of Fluids

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Modification of titanium microstructure after propagation of a melting shock wave (SW) generated by a femtosecond laser pulse is investigated experimentally and analyzed using hydrodynamic and atomistic simulations. Scanning and transmission electron microscopy with analysis of microdiffraction is used to determine the microstructure of modified subsurface layers of titanium. We found that two layers are modified beneath the surface. A top surface polycrystalline layer of nanoscale grains is formed from shock-molten material via rapid crystallization. In a deeper subsurface layer, where the shock-induced melting changes into plastic deformation due to attenuation of SW, the grain structure of solid is considerably affected, which results in a grain size distribution differing from that in the intact titanium. Molecular dynamics simulation of single-crystal titanium reveals that the SW front continues to melt even after its temperature drops below the melting curve Tm(P). The enormous shear stress of ∼12 GPa generated in a narrow SW front leads to free slip of atomic planes, collapse of the crystal lattice, and formation of a supercooled metastable melt. Such melt crystallizes in an unloading tail of SW. The mechanical melting ceases after drop in the shear stress giving rise to the shock-induced plastic deformation. The last process triggers a long-term rearrangement of atomic structures in solid. The overall depth of modified layers is limited by SW attenuation to the Hugoniot elastic limit and can reach several micrometers. The obtained results reveal the basic physical mechanisms of surface hardening of metals by ultrashort laser pulses.

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Laser Shock Wave: The Plasticity and Thickness of the Residual Deformation Layer and the Transition from the Elastoplastic to Elastic Propagation Mode

et al. 2022

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Intense laser radiation leads to irreversible changes in the crystal structure of a target, which are used in laser shock peening technologies. Processes determining the thickness of the residual deformation layer and related residual stresses are studied in this work. It is known that the end of peening is caused by the decaying of the laser shock wave. New information on the transformation of the wave from the elastoplastic to elastic propagation mode under a picosecond impact is obtained. The elastic shock wave is inefficient for peening. The classical configuration with a plastic jump and an elastic precursor ahead of it turns out to disappear during transformation. In this case, the leading edge of the expanding plastic layer gradually decreases its velocity below the bulk velocity of sound, is smeared inside the rarefaction wave, and stops.

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Investigation of the Mechanism of Nanostructuring of Near-Surface Titanium Layers under the Influence of Nanosecond Laser Pulses

Cited by 3 publications

References 8 publications

Melting of Titanium by a Shock Wave Generated by an Intense Femtosecond Laser Pulse

Melting of Titanium by a Shock Wave Generated by an Intense Femtosecond Laser Pulse

Shock-induced melting and crystallization in titanium irradiated by ultrashort laser pulse

Laser Shock Wave: The Plasticity and Thickness of the Residual Deformation Layer and the Transition from the Elastoplastic to Elastic Propagation Mode

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