On the mechanism of deep craters formation under the action of high power ytterbium-fiber laser

31st International Conference on Equations of State for Matter

Kochurin, E.A.^1 ; Lisenkov, V.V.^1,2 ; Osipov, V.V.^1 ; Platonov, V.V.^1 ; Zubarev, N.M.^1,3

Institute of Electrophysics, Ural Branch, Russian Academy of Sciences, Amundsen 106, Ekaterinburg

620016, Russia^1

Ural Federal University, Lenina Avenue 51, Ekaterinburg

620000, Russia^2

Lebedev Physical Institute, Russian Academy of Sciences, Leninsky Avenue 53, Moscow

119991, Russia^3

关键词: Boundary perturbations;    Droplet formation;    Hydrodynamic instabilities;    Melt-vapor interface;    Nanopowder productions;    Spatial and temporal scale;    Tangential discontinuities;    Ytterbium fiber laser;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/774/1/012121/pdf
DOI  :  10.1088/1742-6596/774/1/012121

来源: IOP

【 摘 要 】

Stability of a liquid crater wall formed under the action of an ytterbium-fiber laser in the course of the Nd3+:Y2O3nanopowder production is studied theoretically. It has been shown that hydrodynamic instability can develop on the melt-vapor interface as a result of the tangential discontinuity of the velocity between the vapor stream and molten crater wall. The characteristic spatial and temporal scales are estimated in the framework of the proposed qualitative model, they are found to be 20-90 μm and 20-50 μs, respectively, that is in good agreement with experimental data. Thus, the droplet formation time (during which the amplitude of the boundary perturbation reaches the wavelength order) is much smaller than a pulse duration of the ytterbium-fiber laser (1360 μs). This means that a significant amount of material can be removed from the crater due to formation of microscale droplets during the irradiation. This mechanism can explain the much greater crater depth for the fiber laser than for CO2laser (a pulse duration for which is 370 μs).