Papers by Keyword: Laser Radiation

Abstract: This paper describes a method of laser synthesis of titanium microspheres, titanium carbide and silicon oxide. The formation of microspheres is carried out under the action of femtosecond laser radiation on the surface of the sample. The analysis was carried out on a scanning electron microscope. The obtained titanium and titanium carbide microspheres have an average size of the main fraction of 1-3 μm and can be used in applications of additive technologies and powder metallurgy as the main raw material or as an alloying additive. The main fraction of silicon oxide granules lies in the range of 50-300 nm. To improve the efficiency of the particle output, a combined method of laser action and electric current is proposed.

Abstract: The paper presents the results of an investigation of the influence parameters of laser radiation on the formation of the deposition layer during laser-TIG direct deposition of aluminum wire. Experimental studies have focused on the determination the dependence shape of layer on the laser power, the distance between axis of laser beam and axis of arc, arc parameters. High-speed video recording of the process was carried out. The metallographic analysis of cross-sections of the samples was performed.

Abstract: The process of producing a composite material hybrid powder-laser-casting method. Developed new design of the mixing reactor. On the basis of mathematical methods of modeling examined of hydro-and gas-dynamic conditions for obtaining the suspension of the aluminum melt. Investigated the trajectory of moving particles in gas and liquid flows. Comprehensively studied the regularities of formation and stability of structural phase components in the composite material of aluminum alloy, which was obtained hybrid powder-laser-casting method. We show the possibility to control the porosity of the obtained composite material using the process parameters of the developed hybrid method.

Abstract: The Shubnikov – de Haas magnetoresistance oscillations in the Quantum well (QW) under the influence of confined acoustic phonons, The theoretical results show that the conductivity tensor, the complex magnetic impedance of the magnetic field, the frequency, the amplitude of the laser radiation, the QW width, the temperature of the system and especially the quantum index m characterizes the confinement of the phonon. The amplitude of the oscillations of the Shubnikov-de Haas impedance decreases with the increase of the influence of the confined acoustic phonons. The results for bulk phonons in a QW could be achieved, when m goes to zero. We has been compared with other studies when perform the numerical calculations are also achieved for the GaAs/AlGaAs in the QW. Results show that The Shubnikov-de Haas magnetoresistance oscillations amplitude decrease when phonon confinement effect increasing and when width L of the QW increases to a certain value, The Shubnikov – de Haas magnetoresistance oscillations amplitude completely disappears can not be observed.

Abstract: The metal would overheat and even burn under the thermal shock arisen as laser drilling, which causes micro-damage inside the metal. Cavitation is the most important origin for crack propagation and failure of metal. To understand the damage mechanism in the heat affected zone of the high temperature nickel based superalloy DD6, an experiment of microvoid nucleation was designed and implemented by laser drilling in DD6 sheet. The complex characteristics of micro-damage including microvoid near the perforation were observed by scanning electron microscopy. An analytic solution of the temperature field in DD6 sheet for thermal shock arisen as laser drilling was obtained on the basis of the non-Fourier heat conduction theory. As a result, the minimum of peak temperature during the thermal shock in the zone of microvoid nucleation was estimated, it can be approximately regarded as critical temperature of nucleation.

Abstract: Photovoltage formation across Si and GaAs p-n junctions exposed to laser radiation is experimentally investigated. When the photon energy is lower than semiconductor forbidden energy gap, the photovoltage is found to consist of two components, U=U_f+ U_ph. The first one Uf is fast having polarity of thermoelectromotive force of hot carriers. The second one Uph is slow component of opposite polarity, and it is caused by electron-hole pair generation due to two-photon absorption. Uph was shown to decrease with the rise of radiation wavelength due to diminution of two-photon absorption coefficient with wavelength. Predominance of each separate component in the formation of the net photovoltage depends on both laser wavelength and intensity.

Abstract: In this article, the method of the recovery process of aerospace parts developed. The methodology consists in selecting of multivariate iterative process parameters. Using this methodology can significantly reduce the technological preparation time of production and the proportion of experimental research. Researches of repair annular surfaces pins of gas turbine engine were conducted in order to confirm the developed technique. Appearance reconstructed surfaces studied macro-and microstructural analysis was carried out, as the microhardness of the cross-section thin section cladding measured.

Abstract: In this article, selective laser sintering of fine metal powder of pure Ni with the size fractions 56 ... 80 microns was conducted. Algorithm development process of laser sintering of fine powders was created, allowing to obtain defect-free samples. Investigation of the material structure of obtained samples was carried out.

Abstract: Specific features of electrochemical dissolving of 12X18H9T stainless steel, OT-4 titanium alloy and BK8 hard alloy in the sodium nitrate water solution exposed to 1.06 micrometer wavelength laser irradiation are considered. It is found that the main mechanism of activating the dissolving process is to increase the reactivity of the electrolyte by stepwise photoactivation.

Abstract: The unique properties of laser radiation determine his special technological applications. Surface treatment is a subject of considerable interest at present because it is able to save strategic materials or allow improved components with perfect surfaces. Optical energy is an ideal form of energy for surface treatment. The advantages offered by the laser, the highly localized clean nature of the process, low distortion and high quality of finish demonstrate that. In this paper we will present the main aspects about experimental arrangements for appropriate ideal power distribution to gives a uniform temperature over the area to be treated and metallurgical results and properties of hardened steels.